Well, in the last 2 weeks I've had a couple of episodes where the truck has sputtered pretty bad for a while before finally smoothing out. It always seems to be first thing in the morning too. Today though it was worse and for a longer time. Then, about halfway to work it started to smell like something was burning. It kind of smelled like some electrical or plastic burning smell. But I saw no smoke at all. I had to open the windows all the way it was so bad. The lady behind me was honking and waving her hand so she could smell it too. Then it suddenly smoothed out again and was fine when I got to work. I thought maybe a spark plug wire got burnt but I looked under the hood and everything is fine. The truck is an 88 4Runner 3.0 with 150K miles on the original converter. I thought it would smell like rotten eggs when it went bad but this was a nasty burning electric type smell. I just ran to the post office and it was fine. Oil looks fine, coolant is fine so I don't think it's an engine problem and I never saw any smoke at all. Looks like time to get a bigger downpipe and cat!