1994 Mazda B3000 losing power

My 1994 Mazda B3000 pickup will begin to lose power after being driven for a half hour or so. It gets to where it will not pick up speed and will eventually slow to a crawl. It never dies, and the engine never sounds as if it’s going to die. It’s as if you just took your foot off the gas pedal. I took it to my mechanic and he said the catalytic converters were blocked. After replacing the converters, it started happening again. The truck will rev fine after you pull over and put it in park, but it will only go again after you shut it off for a minute or so. Thanks for any advice.

sounds like a MAF sensor issue, my brother’s F-150 had a similar issue. If you were driving uphill for a long strech, then the problem became much more pronounced and the truck would slow down, slow down some more, and finaly sputter and stop. In his case the MAF sensor was bad causing the ECU to make the truck run way rich. After a while it would start putting way too much fuel in the mixture and it would choke out and die. If you waited an hour or so it would fire back up and you would be on your way for another few miles.