yaright

Here's the problem:

While excelerating in 4th gear ( rpm's at about 2500 to 3000 , speed between 50 and 60 ) my truck starts to shutter...... Doesn't happen in any other gear or if I put it on power.....
At first I was thinking maybe transmission... But I had a mechanic who was working on something un-related and he damaged my MAFS ( mass air flow sensor harness cable ) and it didn't seem to be doing anymore. When I replaced the mass air flow sensor harness cable it started doing it again...... I am completely ignorant so forgive me............Maybe I was just imagining or not noticing it , but there you have it . . Is there something I am overlooking or maybe a common problem...

Any help or ideas would be greatly appreciated... Other then that. I am completely happy with my truck. It's in almost perfect condition with about 252,000 miles on it ( original engine and transmission )