Chugging around 2000 RPM

I have a 2004 Mazda 6 Sport wagon and it seems to chug or sputter (like it is not getting enough gas) when the RPM’s are around 2000. My car has 118,000 miles on it, but it has been doing this sice about 40,000 miles. I have had it into the shop, but the techs can’t seem to replicate the problem. The chugging usually happens when the car is being driven in the morning or after sitting a while.

Get the MAF sensor, throttle body and EGR valve cleaned.
Have the spark plugs, air filter and fuel filter been changed on time? Valves adjusted?
Get a compression test.

All recommended maintainence has been done at the suggested intervals by the Mazda dealer. We are using a K&N airfilter and it too is checked and cleaned regularly. I will have to check into the valve issue, but I do know that a compression test has been done and nothing has been found.
The chugging will happen no matter how warm or cold out it is.

“We are using a K&N airfilter”

Check the condition of the MAF.
Just a bit too much oil on that K&N filter, and you wind up with a gunked-up MAF.

Sounds like its been going on quite a while to be a simple MAF issue. 80,000 miles of this behavior without a big change for the worse is a bit puzzling. You have had no diagnostic codes set? With regular dealer maintainence intervals it sounds like a odd bit of computer software. Did you ask the dealer if the computer was updated with new software? I wonder if the engine is running too rich before it reaches closed loop.

The dealer had hooked the car up to their computer several times and no error codes show. I have not asked the dealer about the computer software. I will call them and ask. The car also has no speed preference on when it chugs, it can be 10 miles an hour or highway speeds. When it is chugging, if you press firmly on the accelerator it will rev up and stop chugging.

That’s great that all recommended regular scheduled maintenance has been done; but, it has little bearing on the problem the car is experiencing, now.
The advice you have received is for procedures which are NOT part of scheduled maintenance. It’s repair action. Yes, cleaning the MAF, and throttle body are REPAIRS.
Even the company which make K & N filters says that oil from the filter can foul the MAF. So, clean the MAF, and throttle body.

“We are using a K&N airfilter”

If it is an oiled K&N, I would put my money on the oiled filter knocking out the MAF.