Hi all! I have a tech question following the replacement of my intake gasket(s) on a 99 Suburban K1500, 5.7l with 132k miles. First, I had coolant leaking at the intake manifold. The coolant was leaking into the oil, but the oil was not milky in the pan, though it was nasty in the valve covers and a little in the lifter valley. The truck was running fine other than the coolant leak. So... I tore it down and replaced the gaskets. Had to replace the EGR tube because it refused to come off the intake. No big deal, right? I cleaned out the covers and places I could see the funkiness in the valley, though I was sure I missed some. I also did a quick adjust on the valves because they were rattling a bit from a while back when I had to replace lifters. Got the engine back together and it started right up. I got a can of GUNK engine flush to clean out the remainder of the nasty oil... I let it run for a bit, drained the oil, replaced the oil and filter. Started the truck up again and let it heat up to operating temp and all seemed fine until the check engine light came on... was an O2 sensor heater circuit error (was getting this before the work too). Again seemed unrelated, just trying to get all the info. So the next day it snowed and I needed to take the Boy Scouts somewhere, so I took the truck. All appeared fine until I got off the highway and stopped at a light... the "check gauges" light came on and I saw the oil pressure was really low and dropped to zero. It came up if I tapped the gas. As soon as the light changed, I turned and pulled over. Checked the oil and the level was fine. I was only a little over a mile from the destination, with no other traffic lights... since the pressure was just below 40 as long as I was not at idle, I went the rest of the way. It was still running fine. We went to leave and the pressure was back to normal... As the engine heated, the pressure went back down. I figured maybe there was some residual engine flush thinning out the oil, so I went home. This morning, I got a new oil filter and more oil. Changed everything again and it seemed better. This afternoon I went to go out for dinner and all seemed fine, but it just didn't sound right. Shifts were too high and there seemed to be less power. I got about 2 miles from the house and stopped at a light and the engine just STOPPED. I pushed it off to the side when it acted like the battery was dead. I had someone come and give me a jump start and got it running, but now the engine really sounded like hell (rattling, kinda knocking, but not like a rod knock... little power and high shift points). Oil pressure was non-existant at idle, but came up near 40psi off-idle. I got it home and stopped in front of the garage and it just died when I stopped. Does it sound like something I might have done incorrectly, or just coincidence that maybe the oil pump failed... or the flush damaged something? I did notice that the volt guage showed lower than normal on the trip home as well. Just wondering if anyone has any clue where to look...? I really need this truck fixed and can't afford to drop it off with a mechanic (they wanted $600 for the intake gasket, which is why I did it myself in 10 degree weather).