2002 Mazda Tribute DX 2.0 4 cylinder, 5 speed man.

3 Months ago the bucking started, only at low rpm while maintaining a constant speed. It did not happen at idle nor acceleration.

The car has 60000 so I did some tune ups. New plugs and wires, PVC valve, still nothing. Cleaned the MAF and things were great. Now it has started again. Clean it and replaced the MAF with a new one,things are still the same as before. When the MAF sensor is unplugged the stutter doesn't seem as bad around 2000 rpm, however it is rough to start.

Were do I go from here: O2 sensor, EGR(removed and looked very clean) , bad MAF still, bad cat, ignition coil?

 

This might be a bit of a long shot, but at least if it's right it's easy to fix, and cheap.
Look for cracks/leaks in the air intake duct between the MAF location and the engine; be very thorough about it because they are sometimes surprisingly hard to see. A stethoscope improvised from a piece of tubing helps to find the telltale hisses from places you can't see.
In many cases where cleaning/replacing air filters/ MAFs etc.etc. has yielded a temporary cure, in fact it's disturbing the inlet air plumbing which temporarily restored the seal, and lo and behold a little while later, like Jason, "I'm ba...aack".
Other than that, get an OBDII readout; and make sure ALL the codes are caught, not just the first one that pops up.
The other thing which can do this is a worn timing belt jumping a tooth. Check your maintenance schedule. I've got a '99 1.8L protege SE and this engine requires belt, idlers, tensioner stuff at 60K intervals.
Your O2 sensors are normally good for about 160K, but sometimes intermittent/dirty connection at the plug can cause problems.

 

the car has not brought up any warning lights also.