I came home last night and raised the hood to see if I could see any sparks because I have a surge, just making sure it was not a bad wire or cap. Then I noticed that the exhaust manifold was red hot. Any reason why this would be.The shop said the timing was right.

 

Clogged cat???

 

No cat been removed

 

Vacuum leak. Makes it run lean, detonate, turn the manifold red if its bad enough at speed/loads. Check your vacuum.

 

Running lean in general. Likely a vacuum leak as said above, so start there, could also be a clogged injector, bad filter, pump going bad.

 

True. Any lean condition will cherry up your headers if its bad enough. But the hunting idle made me think vacuum.