the leak is most likelycoming fromthe fitting connection at the back of the gage, especially if you overtightened it or did not tighten it enough. Did you replace thevacuum lines that you connected the t fitting into? I put my t fitting between the manifold and FPR by the firewall. A leak could be around the t-fitting (did you crack it pushing thevacuum line onto it?)or the lines you connected the t fitting into. check those lines for rot... I doubt a minor leak from the vacuum line on the other side of the intakemanifold would change the vacuum reading that much at the gage, but you never know. If the leak was bad before you installed the gage, you would get a CEL after driving it like that for a while.

 

i checked the lines between the firewall and doesnt seem cracked...i gotta check if its too tight
maybe its too tight...i'll check it out saturday...sending my ECU to get chip. when i get it back saturday i'll run a few tests...thanks for the tips

 

Fixed! now at idle its 20hg..
it was the dv that had the rubber messed up...
i fixed it now its working =)