Thanks for the input guys, I do appreciate it.

It turned out to be the EGR valve. Diagnosis plus replacement was $370. So now I have $1000 in repairs in this thing, plus $5300 to buy it. I know, TMI, but since it's an anonymous forum, why not vent about my stupidity. Also need a new set of tires if I'm going to keep the car which will run around $500 I guess. Recommended repairs today were also fixing the boots on the lower outer control bushings (400) and sealing a leak in the rear differential (600). Do those prices seem really high? They said those aren't urgent repairs and the car probably had at least several thousand miles before they would become urgent. Also said "other than that it's in good shape for a car with 142000 miles." I do trust this shop which is worthwhile even if their prices are on the high side.

I'm headed to a Toyota dealer in the next week to see if they'll give me $2000 or more as a trade in on a new Toyota which is what I obviously should have bought in the first place. The E320 seemed really nice when I test drove it at the dealer but it's turned out to be a lemon. It's one of those things where you get to a place where you have enough money invested in something that you can't back out and go deeper and deeper and I can't afford to do that.

Given my lack of time and ability to do repairs, I can't believe how dumb I was to buy a used car. Reminds me of "The Money Pit" when Tom Hanks is talking to the guy who says "Mister, did you really BUY this house?"