[speeduphoria]

its more hassle then its worth, a stock air box is good past 300whp

If its not turbo just buy a filter and pipe

 

[speeduphoria]

A K&N drop in air filter s a good idea.

You can cut off the muffler, on my Spirit when i first got it it I cut the muffler off and it was still quiet like this, prob because the Cat was original(120K miles)

Basically I would make sure everything is working correctly, meaning new plugs/wires, ect..

Try to get an Intercooler as they help alot, you can make some pipes and put it up front.

Then possibly get a Grainger valve to rasie the boost up to 14psi, you should notice a difference then