If you want big, day-to-day horsepower on a 4banger you are going to have to go with forced-induction or a some kind of stroker job. I'd personally opt for bolt-on, forced induction, since I am no where near close to being an engine builder. If you want power on your 4banger just to compensate for big tires, it sounds like regearing is the smart, though less exciting option.
I do use the Borla cat-back and its been a good product for me.
But does an exhaust or CAI or any of that stuff give you big smiles like some turbo or supercharged car/trucks on acceleration? Nah.
It does sound cool though (which is a nice bonus if you install them on a V8). Frankly I think the bang for the buck on most of the non-forced induction modifications sold for Jeeps, 4 or 6cyl, is pretty weak. But if your stock stuff wears out, why not, right?
The header/exhaust manifold biz is kind of difficult to pin down. Stock manifold is ok for torque but horsepower potential is effected. Seems like the Borla and Banks headers (short tube) provide more horsepower than the stock manifold; but since the tubing on these headers is obviously longer than on the stock manifold,
you'd think torque would improve significantly running these versus stock. Maybe Borla and Banks are underrated for torque improvements?
Then you get in to long-tube headers -- does torque and hp improve across the rev range, 1000-5000rpm -- versus stock? Horsepower for sure. But, Torque? Maybe it does because the exhaust has further to travel? Hard to say.
