I've got a '91 Blazer with the stock EFI 350. Last weekend I took it out on a powerline road, ran it through a pretty big mud hole, and now it doesen't run right. Right after I got through the hole the engine started to run poorly (backfired, lost power, and ran rough when I stepped on the gas), end eventually stalled out on me and I couldn't make it start again. The next day a buddy got me out of there, and when I got back home and tried to start it, it fired right up and ran fine for 10 min and the same thing happened: lost power, runs rough. I removed the distributor cap and cleaned the contacts on the cap and rotor which made no difference. I also replaced the fuel filter. I have no idea what could be wrong because when I first start it it runs fine until it warms up a little. And ideas?