so 3 days ago i put a boost gauge in. i tapped into the line that awe and apr both recomment from the fuel pressure regulator. after a day of driving (probably only 5 hours or driving) the check engine light came on and my boost went from ranging in the 9-11 range to the 4-6 range. i checked the code for the check engine light and it said it was too lean. i disconnected the boost gauge and ran a new vacuum line, and cleared the code and it was fine. why would a boost gauge be causing this problem. there are NO leaks from the tee in to the gauge and the gauge has been tested and is functional. i was told maybe a vaccum reducer is needed?

 

Sounds more like a vacuum leak to me.

 

http://images.google.co.uk/imgres?im...l%3Den%26lr%3D

 

Some prefer connecting to the "P" fitting on the throttle body. Using this connection will not show vacuum on the gauge. The reasoning behind going to the P fitting is that by connecting to the fuel pressure regulator, you run the risk of loosing pressure to the regulator should something happen to the boost gauge hose. The solution is doing a nice job of connecting the hose and keeping it safe. By connecting to the regulator, you will be able to see if the regulator is getting pressure. Nothing showing on the gauge, means nothing getting to the regulator. With the hose connected to the P fitting, you could loose pressure to the regulator and never know. We like the connection shown, it is your choice.

a little from that link seems to describe your problem

 

i concluded its not the gauge. i bypassed the gauge and put it all back to normal. im still getting a check engine light on every few days and the code still says its too lean. my tailpipes are black on the inside which is a huge sign of a vacuum leak. i sprayed every connection with carb cleaner and no reaction. any more suggestions? i had a mechanic look at it and he said definately a vacuum leak but he couldnt find it.

 

hook your boost guage up from the line that runs from the im to the dv.