My 2000 GTS 6-Speed has 270,000 miles and still runs strong with basic maintenance. About once every two months I take it out to the local mountains on this beautiful road called 'The Flowers' which overlooks the pacific ocean through expansive valleys and towering peaks. It has over a hundred hairpin turns, a few long straights, and tons of natural hazards such as falling rocks, deer, and water runoff into the road. It's like an old school arcade racer video game level, and it's the road I first learned how to race on. I first rode it with my father as a teenager in his 427 AC Cobra, drifting literally the entire way to the top carried by the beast's 450 HP 7 liter engine. I in a sense inherited this road from my father and started street racing there just like him after attaining my first car, a Honda Civic LX, and eventually saving up from years of construction work to buy my Celica. The only failure points from this 3000 foot steep vertical elevation climb mountain were the brakes and suspension. While very good, I did get the stock brakes to overheat after reaching glowing cherry red hot and setting the pads literally on fire, but this was at 100% of my effort in second gear down the steepest side of the mountain. Other than that, the brakes shuttered upon braking above 100mph, and they had a vague and unpredictable feel which made it hard to safely brake near the car's limit of traction. I replaced them with EBC rotors in the USR series and am using their YellowStuff pads in the rear and Carbotech XP8 pads in the front. I highly recommend this combination; I've tried **** near every brand over the years and this combo has worked by far the best. You have a temp limit of 1200F before performance suffers at all in the front, and still have bite up to 1500F. If you have a high horsepower Celica, perhaps you'd consider the XP10 or XP12 series, although they will reduce rotor and pad life. The suspension failed on time going down the same steep side after hitting a large series of bumps in the old torn up mountain road. The suspension oscillated like an undamped spring, causing the car to shake violently out of control. That incident nearly took me over a cliff so I couldn't let it happen again. Turns out with hard enough rough road driving, you can foam the shock oil in your struts and make the fluid compressible (air in the foam is compressible), causing the strut to become one giant spring with no dampening, hence oscillating your car with the strut spring uncontrollably. To solve this I went all the way and bought coilovers which I absolutely love, BC Racing's DR series coilovers. I lowered my car 2" in the front and 3" in the rear to even the car with the ground, lower the center of gravity, and increase ground effect. I went with a custom spring rate of 5kg/mm all around, replacing the stock 3kg/mm. People mistakenly try to make their street cars 'like race cars', but that is foolish. Race cars are based around extremely smooth race track surfaces, and hence can get away with things like very hard suspension springs and low ride heights. The same conditions are almost never present on the street, and even a mild speed bump will bottom out a true race car. So, you don't want to emulate a race car, because such settings will not only slow you down, but damage your car and possibly even get you killed if used on the street. Race cars tend to use 20kg/mm rates, far too high for the street. I suggest getting somewhere between 4kg/mm to 6kg/mm depending on how smooth and even the roads you want to go on are. 4kg/mm for extremely bad roads or offroading, and 6kg/mm for very smooth even roads. If you don't drive on the street and will only track it, I'd still lean towards 10 kg/mm instead of 20kg/mm. Rates like 20 can be gotten away with in race cars due to high end features of the strut that the affordable BC Racing coilovers do not have. If you buy their top end series, costing around $5000 a set instead of $1500 for the DR series, perhaps you may consider 20kg/mm for track use. The DR series however is great value and offers a lot for a grand and a half. Mine are still working great 4 years after I got them, so durability isn't a problem, and roads around my town SUCK. So bad people blow their tires out all the time from the bumps and potholes.
Anyway....consider doing that. For engine reliability, you can do a few things. The oil pump is mainly known to blow up if you mis-shift and over-rev the engine to above 8500 rpm. North America redline is 8200, so it won't let you rev high enough to blow up the pump unless you mis-shift, such as while you're redlining it accidentally going into first from second gear instead of going into third, which will rev you to over 10,000 rpm and surely blow up your pump and potentially even engine rods and valves. So, take not to force it over 8200 rpm. You can replace the oil pump with one that can handle 12,000 RPM, made by Monkey Wrench Racing, but it is expensive. Another cheaper option is to replace the valve spring retainers with titanium ones, which will reduce the reciprocating mass and give you an extra 300 rpm safety buffer; not useful for a money shift, but useful on old engines to safely rev to redline. On a very old engine, even the stock redline of 8200 can be too much for the valvetrain. The pump may not blow up, but you can slam a piston into a valve, bend it, or break it off into the cylinder, destroying that cylinder completely. So, valvetrain work is very useful for old engines. You can also replace the valve springs with slightly stronger ones, which will allow you to potentially rev to 9000 rpm with Ti valve spring retainers. This work is complex though, so expert mechanic help is recommended. The cams are known to wear badly on old 2zz engines too, so I'd suggest replacing those while you're there. Don't bother with performance cams, you can only gain 5hp at peak gains; a turbo has a far better hp to dollar ratio. You may also need to replace your rocker arms with the cams. This is prudent preventative maintenance. Be sure to use premium fuel in the car, regular will cause predetonation or reduce horsepower. The oil pan is also a known issue for long high G force turns. I have a Moroso oil pan to prevent this; it's expensive, but you don't have many options here. Aftermarket baffles exist, but you need to professionally weld this to the stock oil pan. Be sure to use high quality synthetic oil at the recommended viscosity. I use Mobile 1. You should also replace the brake fluid with something like Super Blue or Castrol SRF. If you overheat this fluid from heavy braking you can temporarily loose all brake power in your car; it's happened to me on a mountain road and trust me, it's not fun. The $70 a bottle for the Castrol SRF is frankly worth the money considering it may save your life.
2000 GTS 6-speed. Performance Mods: Apexi Power FC, BC Racing DR coilovers, Injen CAI, Catback exhaust, EBC 'USR' rotors, Carbotech XP8 pads, Stoptech brake/clutch lines, Castrol SRF brake fluid, Exedy stage 2 clutch, Mishimoto radiator, Moroso oil pan, 11# flywheel, Braille 11.5# car battery, Energy urethane suspension/motor bushings, BFGoodrich G-force tires.