How can horse power be increased on a 2001 5.3 Chevy engine

New high flow K and N intake filter, larger exhaust tubes a set of long tube headers, if you have the mony a super charger and or a larger throttle body.

I know about how much the intake is but what about exhaust tubes and header? I’m about to but a 2001 Silverado 1500 that has had the motor rebuilt and tranny. I’m a novice at this but $4500 sounds fair even though it has a little bit of rust at bottom of doors.

A supercharger might be the way to go.

Don't know if I can afford that super charger.

Speed costs. The little things will give you little power. Personally I think that the bolt on supercharger set ups are the most cost effective HP gains you can get.