This may be a REALLY DUMB question, but sadly I just don't know the answer. I do have some theories but I'm not sure ... so here goes.

While looking head-on at the throttle body in my 2004 MSM, I noticed that the bottom right of the four bolts (holding the TB to the intake manifold) is missing. If the other three are tight, would there be a vacuum leak?

Either way, I intend to replace the bolt. Does anyone know exactly what kind I need to get? Is that something I'd find in the hardware aisle at Home Depot?

 

One would have to think there would be a leak. Does the car run like there is a leak?

Take one of the other bolts out and measure what you need, buy a new one.

 

I think there might be. Here's what happens (running on the suck-*** stock ECU): when I go into boost / closed loop, AFR is a safe 11/12-ish for most of the powerband, but then it pegs at 10.0 up near redline. Obviously I back off to prevent any damage. So my theory is maybe the missing bolt causes a slight leak which only manifests itself under high pressure (even though it's on the intake side, not the output side?)

 

While making boost there is no chance of a vacuum leak.

Since your running the stock ECU the air is metered and then the motor is told to run with that much air. Since you have a boost leak the motor isn't seeing all of the air and will not run correctly. Also, get standalone.

 

unless the other 3 bolts weren't tight, I wouldn't expect a leak. Pretty easy to determine this for yourself.