[90civichillclimber]

Could be an exhaust leak.

 

[90civichillclimber]

A quick and dirty way to check for exhaust leaks is for someone to block the tail pipe with the engine running while another person listens for leaks.

This is a great way to check for an exhaust leak. Easy too. I mentioned this because it's something a lot of people don't think about before they start throwing parts at a car. The exhaust manifold or header could be cracked. Yes, it fools the computer into thinking it is running lean.