4" Exaust System

[Cobrajet]

I have a 99F250 with a 7.3 PSD and it has a Catalytic Converter on it.
Should I leave it on when I replace the the stock exaust with a
4" exhaust system????
Also what is the best transmission fluid to use???[/quote]

[AYP Tires]

Welcome Cobrajet. So what do ya have a 428CJ? As far as the cat goes it's your call. I took mine out but kept it around incase I need it for vehicle inspection purposes. If you want the best tranny fluid I would go with Red Line or Amsoil.

[Cobrajet]

Yes i have a 1969 Super Cobra Jet and also a 1970 Mach1 along
with my PSD...

Machman

[Worm Drowner]

I pulled my kitty as well. You will be able to hear the turbo spool up much better. I also kept it just in case. Some guys gut theirs, but I would rather leave it alone and pop it back on if necessary.

[99Smokin73Stroker]

Hey Cobra welcome to the forum. I have a 99 as well. I put a magnaflow turbo back exhaust on mine which sounds tremendously awesome with just a muffler only. I have a friend with an 01 that is straight piped and it sounds really good too. I had mine straight piped as well for a while, but it was just cut off right under the cab and had a turndown on it. It got pretty noisy and annoying when the sound bounced all around underneath. I'll run it straight again since it's now exiting behind the tire out towards open air as soon as I find a place around here that can flare a piece of 4" for me. I live in Indiana and we don't have those inspections some of you guys worry about with having removed cats.