I have a 2003 F150 XLT 4.2 auto. I have a Mac intake, Helix power tower, 40 series flowmaster, ground force 2/4 drop kit and I will have the diablo chip within a few days. I am thinking of going to high flow cats or just taking off the rear two. Has anyone tried doing this and how does it work? I'm not trying to lose all my torque but I'm still a little horsepower hungry. Got any ideas?
Thanks
Nthecrux

 

First of all, Welcome To FTE!

Here's the deal with high flows:

I'm interested in getting them also, and I already have the Diablo chip. I've talked with Ken about them and he's told me that the high flows are VERY risky to make your truck run lean because they flow so much. If that happens, you will actually loose power. I think he can program for them but I'm not sure. I would definately call him up and ask him first at motorhaven. Good luck.

 

Ditto what Joseph said: Welcome to FTE!

I would contact Ken at Motorhaven (click upper right where it says PARTS SHOP).
Ask him and see what he thinks about a chip. I'd be afraid you might be too lean otherwise. BUT....I don't know how much correction the OEM programming can adjust for. The MAF, O2 sensors, etc. all tell the computer what is going on so it can adjust the fuel mixture. I just don't know how much it can adjust for w/ stock programming.
Best of luck and keep us posted!
Thanks.

 

I've read that the first two are actually more like preheater to help your cats get hot faster. Would it be better to take them out instead? Also would bigger injectors help the lean out problem? I will try getting a hold of Ken tommorrow. Thanks for the help guys.

 

No you won't need larger injectors. You can remove the preheaters and install high flow cats. The stock system will compensate for that. If you install a chip, you may want to have them add a little fuel thru the fuel curve to be safe since the chip will usually also advance the timing which will cause bad detonation if the mixture is too lean.
My 88 5.0 LX Stang has stock mass-air and has offroad exhaust. No problems, but it has no chip and is pre-OBD-II.