I am looking on buying a early 90's F-150 and just doing the basic bolt-ons like heads, cam, rr, intake?, and so on. I just wanted to know how much hp do I start to get expensive with the speed density bc I know it is pretty sensitive.

 

The amount of horsepower isn't really the limiting factor with speed density. Speed density relies on a vacuum signal to help it determine how much fuel to inject. If you install a high lift cam that effects your idle and your vacuum then you might have problems. If you stay with a mild performance buildup you can run just fine on speed density.

-Jon