[JeremyD]

From the BTDT crew (old 1987)

Steve wong chip, premuffler and sport exhaust
Wheels and tires - 7's and 8's at least (light weight and strong which means fuchs 98% of the the time) Tires can have a huge impact - but they usually also show shortcoming in the stock suspension.
Suspension Elephant racing polybronze or rebel racing - not cheap - but transforms the car - bigger TB
Weight reduction - check out what "shakinjoe" did with his 1987 - dramatic weight reduction and performance increase was astounding.

I really would not bother with SSI's - any other exhaust unless you do cams -

As others have said - upgrading the nut behind the wheel is the biggest return. These cars on the street utilize about 50% of what they are capable of - get on the track - and the light bulb goes off...