Lean condition??

[C5GTO]

Originally Posted by spdbrake

It does look to be lean. But I doubt the exhaust is the issue. The condition was probably already there and the un-coated mild steel exposed the problem.

Typ the VI EFI runs in open-loop when cold and switches to the closed loop feedback once up to temp. AFR feedback being the o2 sensors. And the the system will try and compensate for rich or lean conditions. Are you running O2 sensors? I've seen chipped cars running in Open state full time and that can work but won't respond to AFR changes. I'd get the car back to a Tuner since Bluing that far down the pipes is pretty extreme.

Some helpful info on the Mustang EFI
Mustang FAQ - Wiring & Engine Info
http://www.veryuseful.com/mustang/te...erWorkings.pdf

Last question, that was exhaust tubing that was used and not something like Chainlink fence tubing? Had to ask...

Yes, the car has O2 sensors. In second pic, you can see the sensor just after the collector.

The tubing is exhaust tubing. Specifically, Schoenfeld Exhaust Reducers, 3530. The blue color is on the newly added reducers through the weld and onto the existing sidepipe tubing where I removed the ceramic coating to weld.