ive allready done the exhaust on my 91 silverado ... i was wondering if the helix throttle body spacer will help ??? and how much power will it gain??? and also the k&n intake system the giude shows 2 different systems .... which one ??? any help is greatly appreciated...

 

Throttle Body Spacer - I bought one on eBay and put it on. The air made a nifty noise when you hit the gas. It made a 20% difference in mileage. MPG went from 16.8 to 13.6. I took it back off and sold it after two days.MPG went back up to 16-17. If you really want to try one, look on eBay. There's lots of them for sale there pretty cheap.