I have a 92 Flareside 5.0L w/AOD tranny. The engine seems to have a miss throughout the rpm range and struggles going up hills and bridges. I have to shift out of OD to compensate. I had my local Ford dealer run a diagnostics and was told that I have low compression in one cylinder. The truck has 119K miles on it. There is also a sucking noise that I hear when I turn the engine off. It lasts for a few seconds and dissipates as pressures are equalized. It sounds like a vacuum leak but I'll be darned if I can find it.

I want to check compression to verify the Ford dealers findings but the manual (Haynes) I have does not address it.

I would also like to know how the engine would be affected if the catalytic converter is restricting exhaust flow. How would the conditions be manifested? I know that restriced flow will have detrimental effects but have never experienced them.

I appreciate any words of wisdom.