1988 LO3 V8 was TBI with 170hp 255lb tq and was avaliable on IROC-Z, Formula and Trans Ams.

(anyone that doesn't believe me refer to this http://www.thirdgen.org/newdesign/tech/techdb.shtml )

My number 1 suggestion would be headers, and a K&N for the air cleaner. A friend of mine has a 89 Trans Am TBI, has the same motor and headers and a high flow down pipe and muffeler really made a big difference.