I have a 04 5.4L with flowmaster exhaust, K&N Intake, Throttle body spacer, and SCT programmer. Just trying to see what everyone thought would be best thing to do next. I was thinkin about getting a performance catalytic converter but not sure.

 

supercharger lol!!

 

I cant do anything that serious until my warranty is up lol

 

Well if you upgraded the exhaust already you might want to try upgrading to better headers as well.

 

sts turbo

it wont void ur warranty
or a professionally installed by ford roushcharger wont void it either

 

any ideas on how much new catalytic converter and/or new headers would improve my performance

 

cats are a good upgrade, good stuff are the magnaflow high-flows.

headers are only good for the top end perf and not good for anything low end. they dont improve tq or hp too much.