You do not need cats to run. They are for emissions. What is being suggested is that by removing the cats you removed restrictions in the exhaust and that may be causing you to run lean because of the now freer flowing exhaust. The 4.6 is designed to run a 4.6 engine. Because the 5.4 has a longer stroke the engine timing has to be adjusted to compensate for the faster piston speed. The 4.6 is not set up to control this engine but it can limp along till you get a tune. The removal of the cats compounds the issue.

Did you use the 5.4 torque converter or the 4.6 converter? Get the codes scanned so you at least have an idea of what is going on. I suspect that at the very least you will have codes for the rear O2 sensors. Lack of switching and heater circuit if you left them unplugged.

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you dont necessarily need cats, but the engine does need a little bit of backpressure, and without them you could possibly warp valves. plus you wont get in so much trouble if you get pulled over by a cop or if you need an inspection done. the rear o2's only monitor emmisions but the front ones control the A/F ratio.

 

ok well i welded in the rear two 02's yesterday.. and i shouldnt have a problem with the cops becasue there is no emissions in ohio. also made a appointment to get it tuned on thursday... you guys think i should get a tuner or get it flash tuned

 

A competent tuner can set you up with either a chip or a flash device. They both get the job done. I have had 3 different forms of a tune. A single chip, a flash chip ( holds 4 tunes) and now a Flash device ( holds 3 tunes). I prefer the flip chip. Turn the **** and the tune changes instantly.


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