Backfire through intake

The old plugs looked good. Don't know what MDS means. Do injectors get bad or do the clog up.

I have a 1994 dodge ram 1500 with a 318 in it. I replaced the plugs, wires, coil and yesterday I replace the cap and rotor. When I'm driving in normal traffic it runs good, but when I take it on the high way or go over 50 mph it begins to spit, sputter and then backfire. Before replace the part above it would only spit and sputter at high speed. I checked the fuel pump and it checks at 40psi. Now I wondering what could be causing this?

Yes. And I notice the backfire when I let off the gas pedal

2000 Dodge Ram 1500 4x4 5.9l, the problem is that it wont start, it was running "fine" I got gas at a station I normally dont but the price was right, ever since then it has backfired several times, tonight I was sitting at a train stop and when the gates lifted I took off normal and it started sputtering and backfiring about half way over the tracks, then it died and wont start again. At first it sounded like it was going to start and then, after I pushed it off the road more, it doesnt even try to start. Im thinking maybe distributor but im not sure how to check for spark and all that, I dont know much about cars but I am mechanically inclined.

Well I think I will check the spark in the morning and see if it is getting any, if not I will assume the distributor is bad. I can hear the fuel pump coming on and I pressed the pin in the connection on the fuel rail and it sprayed out. Dont know if that means anything im assuming it has to be a certain pressure coming out.

Ok so I took it to a guy and he hooked it up to his computer scanner, he says it said the main computer (ECM/ECU?) Is bad, does that sound right or possible, btw I pulled the wire from the coil tower to the distributor and got spark, so I put that back and pulled 3 plug wires and got no spark, pulled the wire off the coil side and got nothing.

Just wondering where the start. When I accelerate at more than half throttle the engine backfires, it is not herd at less than half. Seems to happen right when I accelerate but goes away when the RPM get high. Have not noticed it after running down the road and 70 then going up a hill and down shifting.
Tested fuel psi and was 60-61psi at an idle no check engine light on. The colder the engine it happens more. Warmer outside air seems to make a difference, warmer backfires less.

Have found the problem it was the spark plugs I am guessing that they had not ever been changed 125000mi is a bit long. Spec was 30 and they measured 60 now is running good.