Ok so I just replaced the thermostat housing because it was leaking and now after driving the car for a few days, the HALF CEL comes up when the car is cold and only when in boost. When the car is cold, boost seems to build up more slowly than it did before and only gets to about 5 psi. Here is the weird part: the HALF CEL goes away when the car is warm and only when in boost. Once the car is warm, I max out at around 11 psi and the HALF CEL goes away but only when I go up to 11 psi otherwise it stays on after boosting for the first time when car is cold. I was thinking this problem could be due to an air leak in the vac system but I triple checked the hoses and clamps and all seems well. Any help would be appreciated!

Mods: boost gauge, bov adapter, k&n intake, invidia q300 catback

 

Did you check the wire harness and the connection to the turbo and vacuum lines ? You might have bumped them.

 

Yes, I took off the entire intake and rechecked the wires and the vac lines, I even pulled the vac line covers off and checked the connections within the lines..

Could this whole issue be caused by a bad vac pump? How could I check if the pump is bad?

I had the half cel come on before but that was because this vac line (yellow zip tie) wasn't on correctly:

P.S. this hose was drenched with oil when i took it off a while back, inside the hose and outside

 

turns out that it was the other end of the hose with the yellow zip tie above that was loose

i jacked up the car to follow where the line went and after making sure it was in right at both ends, the half cel never came back and boost seems like it back to normal

this thread was a good reference (post #14):
https://www.northamericanmotoring.co...ach-issue.html