PCM tuning for exhaust setup?

[99Merc]

Hi guys. I've been racking my brain doing searches for this kind of topic, but haven't really gotten what I'm looking for.

Let's say, hypothetically, I'm building a track-only MGM. Now, never being an EFI guy, I can't quite figure this out. Some of these questions can probably be answered with the same response.

1) If I run only pipe and mufflers from the manifolds back, and weld in bungs for both sets of 02 sensors, will the lack of cats cause my computer to start dumping fuel to compensate for the increased exhaust flow?

2) If so, taking it to a dyno shop will obviously fix that, right?

3) I've heard that I don't even really need the second set no matter what and that I can have a shop "turn them off"?

Like I've stated, I'm new to EFI and while I can service and understand nearly any part of the EFI system, when it comes to the effects that doing certain mods may have on my engine management (like a cat-less exhaust), I'm at just a little bit of a loss.

Thanks folks.

Sam

[ImpalaSlayer]

well i know for a fact the rears can be turned off.

on my set up i have both sets still installed but the rears are turned off.

also, i have kooks headers and the upstream sensor bung is welded into the collector and the down stream is behind the cat (only one set of cats now). but like i said before the rear sensors are turned off. so as long as the rears are turned off you should be good to go!

[99Merc]

Thanks for the advice!

[Vortech347]

You will need a Tune if you alter the distance between the exhaust pulse's and the O2 readings.