>I'm not sure if this is worth it, so I have a few questions:
-can you upgrade to a bigger turbo
-would you benefit from a free flowing exhaust (i.e. headers,3" exhaust)
-how much boost do you loose when going through an intercooler?

 

BTW this is for my Silverado I'd rather do a twin turbo setup for it, but where can you find one?

 

Yes you can upgrade to a larger turbo and STS does offer many turbo upgrades. I am running the STS kit with OEM manifolds and 3" catless exhaust system and it spools great.

I have heard that headers will not make enough difference to actually spend that much on them but it is the vehicle owners choice.

I am not running an intercooler at this time but from what others say with coolers that you really wont notice the difference as a negative but more of a gain.