I am swapping my 305 TPI for a Zz4 motor. I have been researching carb vs keeping my TPI system. Since my TPI is an 85 it sounds like it should just mount up, although it sounds like it is the primitive system. Would it be better just switching to a Holley carb, mounting my current system or going with a different fuel injection system. Emissions are not an issue in my state and I will be eliminating my cat and installing headers. I would really love to run a true dual exhaust but in reading that sounds like a nightmare and am better going with a aftermarket exhaust and run a 3” pipe. I want it to sound more beefy than stock but not much louder. Thanks for your input.

 

The 85 tpi is the most primitive ecu for multiport injection. It can be converted to the 86 and later ecu. Can also move to EBL, Holley, Megasquirt or whoever and tune without changing the whole system completely. The factory tpi will severely diminish a zz4 compared to a carb or FIRST or HSR or just about anything.
IMO switching to any of those is just about the same amount of work to convert to a carb. I'd personally rather keep an efi car, efi.
How loud it is mostly depends on the muffler you're using. 420 hp can still be relativly quiet. Flow and noise, while related aren't mutually exclusive.

 

Google Mike Davis ZZ4. “My 85 Z28 and EPROM Project”