GM-GMC: 1997 Chevy V-6 acceleration, speed increase, wd

Question
 Hey, my [1997 Chevy V-6,1500,2 wd, auto trans] got a rebuilt engine last year...recently it'll refuse to accelerate...it starts, runs and I can coax it up to 75-80 mph but that takes awhile...I can no longer just punch the pedal...instead it bogs down...
 It cruises along at 1500-2000 rpm and when I depress the gas it jumps to 2800+ for just a moment with no corresponding shift of the transmission or speed increase and then falters...so I ease up and nurse it along and wait for a down-grade in order to speed up.
 One time the service engine light (which has been on for months)started flashing and then stopped when I backed off on the gas...any insights? (thanks!)

Answer
This is not really my expertise unless I am able to see the vehicle. Also if it does not have the original engine there may be a possibility that the transmission is causing this issue.

I can only advise to take this to a "roadside" mechanic that you trust and have them look at it.