Not too much to make them fast. Mine was $5000 when I bought it in 1995. Went 12.20's@110.5 with stock turbo, intercooler, injectors, 100% stock 88K mile motor, transmission, body, rearend, wheels and drag radials. upgraded injectors to 36# blue tops, turbo to TA49, Welded a larger neck on the stock intercooler and have gone 11.53@118 on drag radials thru a $250 mufflershop dual exhaust .
Motor and transimission original and untouched with 95K miles.
Mostly tweaks and low buck mods and the ability to listen to your car and tune appropriately. My '89 LX5.0 Convert went 13.5's with the same free/low buck tuning mods my T-type went 12.20's with. Both cars respond to free mods, T-R's repond better.