2010 a4 2.0

[Bobstks]

Trying to figure out why it idles up and down when I'm sitting, loke at a light but if I put ut up in neutral it doesn't do it?

[jessenepywoda]

Could be many many different things. I would catch up on all your maintenance items, make sure all the charge pipes are clamped down securely, and inspect vacuum hoses for leaks. If you have not replaced the PCV valve ever, that could be it. Lastly, getting a VCDS scanner will help you diagnose problems.