Besides forced induction what would be the cheapest way to increase a 91 silverado's HP by 100.Any help is appreciated greatly

A Westers tune can increse your HP by about 40 at a fractoin of the cost.

pully kit, new intake, headers, exhaust, removing weight, racing cams, gears, porting heads and cylinders, crank shafts, heads, port & polish. many more parts do some research and you will reach the power you want. [sm=massbounce.gif]

this is what i did to my 2004 4.3 w/t to boost hp alittle
http://img190.imageshack.us/img190/8030/toys0019fv.jpg

http://img190.imageshack.us/img190/5694/toys0025dp.jpg

well the cheapest way would be NO2 but from my own experince in the end it can cost as much as a new engine.

just remember that NO2 is like a hot girl with herpes you want to do it but your afraid of the consequences