My check engine light came on. Took it to Autozone and had them run a diagnostic check on it. The code said that exhaust manifold runner controls banks 1 and 2 were stuck open. The light went off later that day, but came back on today. Thanks for any help.

 

I think you have a V6 engine.
There are no exhaust controls but there are ' intake runner ' controls (IMRC) that get stuck open.
This condition would reduce the low end performance.
Codes would have been p1537 and 38.

 

Sorry. You're right it's intake runner controls. The code is a P1537. It says bank 1 and 2. The light was off for a week and them came back on for about a day. It's gone back off again. By low end performane you mean low gears? I do alot of stopping and starting.

 

Low end means lower rpm range.
The IMRC operation changes the intake runner airflow tuning by an external control system.
At lower rpm the manifold runners are made smaller to airflow, to keep the air speed up which helps cylinder filling then the IMRC opens a second path adding airflow volume at the higher engine speeds.
Yours system has an operational sticking problem.

As a side note, the stock exhaust and muffler is a factory design that gets the best overall exhaust extraction from these motors as well as the 4.6/5.4 sizes and is why most all after market systems lose lower rpm 'pulling power' except for one system well known on this board.