did a test on my map sensor with the vacume pump rental tool at advance auto parts. the vavume and voltages matched what the specs showes thet should be.

i used 2 scantools mine and a friends and they both show 8inhg at idle but a vacume gauge hooked up to the booster hose shows 19inhg at idle

so why is the output voltage correct for the vacume but the scan tools show different


issue is strange power band and rough idle (new iac do to last one totaly failing)

 

what change am i looking for when i apply vacuum to the regulator?

and how does that affect the vacuum?