I'm in California the state of no fun engine mods but I know there are options out there I was looking to up my HP a little so I don't have to change out the back end and transmission It a 305 stock except for a flowmaster cat back. I was looking in to trick flow 56 cc heads and a set of new headers but I need to keep factory ECM and EGR for smog (Also would love to keep AC) a little help

 

Can't do TBI without the ECM. Headers don't affect EGR. So no problem there.

You do have AIR if memory serves, which must be preserved of course. The headers will need to have the fittings / pipes / whatever for that.

Dyno Don is out there in OC; might have a variant that would take care of you. That, a larger cat (for TPI 350 maybe), and a cat-back exhaust, all with CARB EO #s of course, should fix you up. Whatever you do, DO NOT get anything that will bolt up to your existing stock exhaust, if you can AT ALL help it!!! Every single piece of that coffee-stirrer thing needs to GO AWAY, from the heads to the street. Anything that bolts to it will retain its tiny restrictive poodle-d*** lack of size.