On the base manifold, TPIS big mouth there are holes, 4 of them, in between the injector bosses. I am wondering if they cause a vacuum leak if left open. I was reading a back issue of a magazine that the Accel base manifold has similar holes and according to them if the holes are left unplugged they will cause a vacuum leak.

I am wondering about the TPIS piece because I noticed on a scanner that the vacuum is showing at idle 14 inches of vacuum. That is much lower than I would expect with the cam and other componets of my engine. I would think the engines would have 16-17 inches of vacuum at idle.

If anyone has any idea about these holes let me know

THanks in advance.

 

i would take a mechanical vacuum gauge to verify the vacuum you are getting.

 

Do you have a picture of these things? I'm wondering if they are the 4 holes that the studs that hold the fuel injector harnesses in place go into.

 

I don't think so because my factory manifold doesn't have anything like that. My harness has a hold down that uses a different hole. These are very small, maybe a 1/16 of an inch or so in diameter.