2004 Chevy Venture hesitation

2004 chevy venture with 82000 miles. On the highway engine hesitates for a brief second. Engine and transmission seems to run fine otherwise, smooth, with no problems with town driving. Service engine light was on and took it to our local mechanic. Code came up for the Mass Air Flow sensor. Took it apart, clean the sensor and the area around it, and new air and fuel filter as well as adding fuel injector cleaner and new gas. Check engine light went out (is still out today). Didn't seem to help. Replace MAF with a remanufactured one which resulted in little to no help. Replace throttle posiition sensor which resulted in little to no help. Just replace idle sensor along with plugs and wires. Seems a little better but still not right. Taking it to yet another mechanic (GM dealer) to see if the can pull a code. Totally frustrated. Crank position sensor? Catalytic plugged? I have to think it's something not plugged into the computer since no service codes are cmoing up.