boggin issue

buddy of mine has a 84 mazda b2200 truck runs and idles fine you can run it up to redline but when driving the truck you get up to about 30-35 miles and hour and it just boggs out like a governor is kicking in..... anyone have any ideas of what could be causing this?

no governor in these trucks???? sounds like a fuel delivery malfunction. check your fuel filter. whens the last time the truck had a full tune up? also how many miles on the truck? any preformance parts??