Ive got a 98 Hoe i bought from a buy here pay here lot, bought the service plan they offered for $200, covers most major parts, seals, and other stuff for 5 mos 5500 miles. Well driving a good distance approx. 100 miles or so it started misfiring and the CEL started flashing. Found po300 and p0420 codes. hooked tech two up and verified cylinders 5 and 7 were misfiring under a load. Replaced all the usual suspects, cap, rotor, plugs, and drove it home from work. still misfiring. Returned to work the next day and pulled out 5 and 7 found them white on the electrodes, which made me suspect they were burning coolant. Stall tested it while it was hot and it began to misfire on cylinders 5 and 7 after about 10 seconds or so, and began to spit coolant from under the rad cap and gurgling into the overflow canister. Compression test was fine running and just turning it over, did use a block tester on the radiator cap and it failed, meaning exhaust gases are getting in to the cooling system. I believed it to be a head or a head gasket problem, called them, and of course they have to have their guy look at it and yada yada. Told them everything i did and what the problem was on wed, and they called me on friday to tell me that their guy said it was just the intake gaskets, and that they would be covered. Got it back today @530 and brought it home after driving it a while i pulle dover and stall tested it.........you can guess what happened next....after about ten seconds spitting coolant out of the radiator cap, gurgling, and missing its A$$ off.......anyone else think it might have a head or head gasket problem??