Lets solve this!!

[Solo79]

I don't think it's the map sensor but here you go.
http://troubleshootmyvehicle.com/gm/4.3L-5.0L-5.7L/how-to-test-the-map-sensor-1

Thanks allot!! This was interesting reading, have a vacuum pump so will measure this weekend.

 

[Solo79]

Measured the MAP and got DC 4.03 on green cable Whit ignition on, when turning on the vacuum pump attached to MAP I got a decline to 0.99-1.00. It looks okay but can somebody confirm this numbers. Thanks.