Ok nieto just helped me install boost gauge and my vac at idle is at - 20, and when the ac is on it goes to 18. i notice that the idle goes up when the ac is on. Under full throttle it reads 12-9 -13 for a sec then it holds at 12. I thought the vac should be 18 at idle. My mods are greddy smic,apexi intake, downpipe,m2 stage 3 ecu rb catback,i am running the stock cat. The car used to idle at 800 rpm when it was stock, now its like 600,should i adjust the idle screw. Do i have a vac leak since it reads -20 at idle

 

mine reads from 20 to 18 on different days.... doesnt seem to affect hp at all. I would consider getting rid of the stock cat, and put the midpipe in. its like a whole different car with it out. you already have the ecu for it so give it a shot.

 

I dont want to smell any gas fumes,and i do feel a little safer (richer) using the stock cat.