2001 Ford F-150 SuperCrew with 3 Inch Cat Back Exhaust and I lost Back Compression.?

It's called back pressure and with out it you lose low end torque. That means you now have a slow dog off the line! It happened to me when I put headers on my Grand Prix GTP. I was fortunate that the motor was supercharged. I put a 3.0" pulley on the supercharger and it compensated for it. If you don't want to go back to the old exhaust you can either put a more aggressive cam in the motor or try making a restricter plate for in the exhaust. Try two gaskets after the converter with a metal cut out plate 3/8" smaller in diameter than the gaskets sandwiched between them.

1. It's back pressure, not back compression

2. With a cat back system you didn't lose much back pressure since the cats are the major restriction anyway.

3. If you have a lack of power, then there's something else wrong with the engine, but chances are it's not the exhaust.

2001 F150 Exhaust