I had the same thing happen to me. I found a smal tear in the air tube after the MAF sensor and before the throttle body. Whent he engine flexed under load it would open up the tear and cause "extra" air to enter the engine. the MAF snesor would say one thing and the amount of air would be different.
On car number two same problem, found the seal around the air cleaner box was not sealing outside air and allowing more air by it. changed seal around air box problem solved.
look at your air tube and all its connections between maf and throttle body.