Rough Running

I have a Mazda 4x4 2600i that has started really running rough...Wield rock at idle. Ive done all the normal things...Cap/Rotor/Plugs and wires and went to far as to have AvPro look at both my ECM and a spare. The ignition timing is fine and I have no CEL.

The exhaust note sounds like its chugging.
The lifters are quiet and it does not appear to be burning oil.

The ONLY thing that has changed is I had the truck painted and they dis attached the bed to slide it back. Is there anything under there they could have screwed up to make this happen?

I'm really stumped.

Finally have my truck running sweet. Let me tell you, I was really chasing my tail! Initially I had lots of hesitaion and backfiring. I replaced the plugs, wires and cap and it still ran like crap. It idled but was hard to start and hesitated on acceleration. Next step was to have the ECM check...Bad as suspected. Avpro did a nice job. Reinstalled the ECM and it ran better but like it was missing a cylinder and every once in a while it backfired. WTF right? I pulled the plugs and cleaned them and it ran better yet but still chugged. Finally, I decided to buy a cheap set of NGK standard resistor plugs instead of the Bosch quad platnum ones and it fired up silky smooth. Runs AWESOME. Hard as it is to believe, I think the bad ECM actually damaged the plugs or they just don't work well in our trucks.

Man...what a challange this thing has been! I still love it though. Its fun owning a truck you donlt see on the roads anymore in New England. They have all long since dissolved in the northeast salty winters....

Bosch plugs run like crap in these trucks.
They are designed for German Vehicles.
A good rule of thumb is any Japanese vehicles use NGK plugs

did this start after the moved the bed back? could be a pinched fuel line. could also be the catalytic converter stopping up.

Cat is new and I checked fuel lines. Truck is running mint now. I don't recall it ever running this smooth.
Thanks!

what ended up being wrong with it?

At the root was a bad ECM.

But before I knew that I thought it needed plugs. I replaced the plugs, wires, fuel filter but still ran like shit. black smoke and backfiring. Sent ECM to Avpro and they did their magic and I reinstalled it...It ran differently but was jumping all over the place at idle.

Bottom line is I ruined the plugs running the bad ECM and once i replaced them again, it ran flawlessly.

Good to hear it was fixed