When you start the car and it is idleing, What is it suppose to read on the turbo gauge?

 

Boost gauge I'm assuming....

If the car is idling, it should read in the vacuum (if your gauge has vacuum reading):

Normal stock motor will show 18" or better.
Mildly ported motors show 14"-16".
Heavily ported motors can go down to 10"-12".

Of course, those readings will vary depending on idle rpms, altitude, etc...

 

A few weeeks ago it was showing 18" now it's at 20". Is that okay? What's the first sign that you get when your turbo's go bad?

 

The vacuum reading won't give you an indication of the turbos going bad. When the turbos go bad, you see usually one or more of the following problems:

* low boost
* pool of oil in the intercooler
* smoke pouring out of the exhaust while boosting