? I got a chip for a 96 F150 5L 5 Spd truck, maybe it will work...is there a sticker on the door jam of your truck that has a Calibration Code number...if it is the same as my old truck than it's 20HP for a $100, I also have a K&N that will fit your factory airbox that is good for another 5HP at least.
Ford factory manifolds are quite restrictive. Talk to the guys at mopac. They can point out which header will work best.
Go with the 3" pipe. The cat and bends in the pipe will generate enough backpressure.
'94 XJ - 3" RE lift, 31 Big O XT
'97 F250 HD 5" custom lift, 33" BFG AT