I have an 02 Xtreme Blazer with 118,000 miles on it, it has good oil pressure when cold and even once it get warmed up. The other day after driving about 40 miles and sitting idling with outside temps about 85 degrees, I was losing oil pressure at idle. It was running at 4-5 psi then would occasionally drop to nothing especially when running the A/C. I’m running 10-30 in it for oil now. I was thinking a weak oil pump or even worst worn crankshaft bearings. Any ideas??? Plus I have an misfire on cylinder 4 which I think could be this dumb injection spider. It has new cap, rotor, plugs, wires, and I have done a compression test which tested fine. I’m thinking about swapping to a marine intake cause this engine may see some kinda boost in the very near future.