vacuum

I am having issues with loping and surging at lower rpm's, Maybe at higher but can't tell. Someone said that I might be having a vacuum leak, 1986 2.8 V6. My vacuum is 15 at idle and drops when throttle opened then recovers slowly. I hear a small whistle sound when I let go of the throttle, need to get a better stethoscope, I can't pinpoint it yet. How do you check the throttle body- MPFI- for leaks and how do you rebuild them, can they be?
My mileage is good but inconsistent as with the power or so I believe about the power. I am convinced now that my computer setup is ok and my sensors are doing what they are suppose to.

Normally a lopey idle is from retarded timing.

Finding a Vacuum leak is the same
process as an MG

I think i found it, I hear whisting noise from around the front/bottom lower piece of the intake manifold and the couple of hold down bolts were a little loose. I am going to take the top off and re-tighten all of them. Maybe because of dissimilar materials they need to be re tightened after they run for awhile

Start the engine and try spraying some ether at the suspected leak point- any leak will show up as a momentary increased engine speed.