After i install my K&N open aircleaner, TES headers, Catco converter, Flowmaster cat-back, and 3.73 gears w/posi, WHATS NEXT?, i was thinking about getting a new cam, piston, port and polish the heads, and upgrade the intake manifolds and TBI, which of these should i do first?

1990 RS TBI

 

Intake manifold, otherwise you should do all of them at the same time. You're gonna have to take it off to do the other ones, anyway.