Anyone have any info on doing mods to Prodrive 37EFI..
I don't really want to do any major mods to the engine, but was thinking about helping out air flow at the very least. Thought about getting a Q muffler and putting K&N air filter on it help breathe better. Is it worth the $450 or so for the muffler and putting new air filter on . I know if wouldn't notice much, just curious if anyone has the same stock motor and added a Q muffler to it.

the air filter is a waste. The first thing you should do to any engine is get a set of heads that are ported (I prefer smaller porting), stainless valves, decking (to boost compression), and a good valve job that seals the new valves to the seats. This and a cam swap are the most bang for the buck, and they work well together.