Chevrolet Repair: Engine Noise, cat converter, check oil

Question
I've got a 4x4 1988 K5 Blazer with TBI 350. A couple of days ago I got in my truck to run some errands and everytime I stepped on the gas, it made a knocking sound. It sounded like it was right in front of my in the engine. When I took my foot off the gas, it would stop, but the truck doesn't have as much power as it should. Help? Advice?

Answer
Hi Miranda... could be a couple of things... first check cat converter and see if plugged, second check for timing chain gone bad, third check oil pressure, if below 5 lbs you could have bottom end problem...best bet would be to have a qualified tech, look at it...hope this helps.