What kind of improvements would i see by using a Skunk2 pro series intake manifold alongside my CAI and an optimised exhaust (good header, decat and catback) on the stock engine setup?

 

probably good for about up to 20 hp depending on the company.

 

Is the intakemanifold change worth the effort then, is it significant enoughin itself?

 

well, if an intake mani costs $500 and it gains 20hp, that's $25 for each horsepower you gain. Personally, I think it's worth it (especially when you consider that an intake would be around $33/hp, aheader would be $50/hp, and an exhaust would be $100/hp = rough estimates).

I say go for it... when I swap my engine, an aftermarketintake manifold is going to be on the engine before the thing's even in my enginebay.