I have a custom chip made for my car when it had the mods in my sig by a performance shop that tuned it by a dyno and laptop. Im going to be putting on a set of heads but dont know if my chip will have to be redone or if it will be fine the way it is. Here's the specs on the heads, its from an ebay listing:

"1989 Chevrolet GM Camaro Firebird Trans Am Z28 heads casting number 14102187. They have had extensive work done at a local machine shop, no corners cut. Exhaust valves have been re beaded in the correct way. Oversized valves 1.98 Intake Valves 1.60 Exhaust valves K-line bronze valve guides. Fresh from the machine shop valve grind never fired on included are pictures where you can see teh vavle grind with the marker still there so you can see contact points. Pocket porting was done when the vavlves were enlarged and they were decked. The decking is good for 1 full compression point when used in conjunction with stock head gaskets for an 1989 Camaro z28...So here you have it folks. Decked, Ported, Machined for oversized valves, Ported, the works all on the performance factory 305 head. Very trick part good for more power... and thats what its all about isnt it. Advantage here is that they have a completely stock appearance.
These are the 58 cc chambered heads in theory you could bolt them up to a 350 and jack you compression through the roof or a 383 or a 400 334 283 327 307 corvette whatever you want"

 

Probably won't need changes, mostly due to this being a MAF system. How much difference are the new heads vs. the current heads?

RBob.

 

the heads i have now are just crappy stock ones. Dyno2000 said my car currently has about 260HP and 305TQ (flywheel) wich is about right with my mods. With the heads it boosted it up to 315HP and 420TQ and with headers it will be 355HP and 455TQ. So there's quite a difference but we'll see once there on.