REVZ

I'd been driving around for a few months with my new headers and everything was fine. I got some cats put on and straight away the problem started.

When I start the engine cold it idles very loud. Not a good loud either mind you. A vibrating sub-woofer rattle your bones kind of loud. It is very annoying for the passengers and sounds crappy from the outside. Funny thing is the RPM's don't seem any higher.

As soon as I get up to speed it goes away. If I stop the car and start it again it's okay. It only seems to be when its cold.

I tried a PCM reset and idle relearn but it didn't make a difference.

When I start the car with the A/C on the vibration is almost unoticable.

Any ideas what I can do to fix this? I haven't had the dyno tune done for my headers yet. Would now be a good idea? Do you think it will fix this? Also do I run the risk of ruining my plugs & cats by running rich at WOT without the tune?

Thanks