92 Stealth R/T-One pissed off owner

[hink12341234]

92 Stealth R/T with the DOHC engine and 5sp manual. This car has not ran right for almost a year now. About a month ago I decided to give that problem a rest and get this car in showroom condition. I fixed "every" paint chip to the point where I took 2000 grit sandpaper to each one,rubbed them out and they came out perfect.
The paint on this Stealth held up very well. The paint is 15 years old but with a little work it still looks new. Right now the car is perfect except for "1" big problem. This car simply will not run right. It has a slight miss and it's there through all RPM ranges. I just got done taking the ISC/IAC servo out and giving it a good cleaning and this did nothing to help the miss. One thing has changed though in the past week.
When you are going any speed and you take your foot off the gas and your coasting the engine "will" backfire now. There not loud but very noticable. Took it to a mechanic and no codes came up,compression was good and no vacuum leaks. I'm simply lost. With the backfiring any ideas? Thanks for the help!

[VR43000GT]

Backfiring means you may very well be running rich. Check you A/F ratio.

[Linebckr49]

too bad there's no way to check the a/f ratio on a stock car.

you will want to check your plugs, wires, o2 sensor. those are good things to change as far as getting your car running right. also, fuel filter, air filter.

[VR43000GT]

You could buy a guage for approx $40 give or take. But yes, check the above.

[hink12341234]

The following is new-plugs,wires,02 sensor,injectors sent in and rebuilt,they were ok to begin with,with other engine I swapped the 3 coil packs,new coolant sensor,keep in mind the CEL has never come on. It's not burnt out. Pulled fault codes with multi-meter,again no codes. I have the CAS from other engine. Will swap that also. You mention air fuel mixture. How on earth do I check that? If it's a faulty MAF sensor it SHOULD trip the CEL. Am I wrong here? Running this bad it should trip the CEL. Since it doesn't what's the point of the CEL in the first place. Fed up with it. I refuse to start "throwing" parts at it. No car is worth that. Once again the air/fuel mixture sounds like the problem. How do I fix it though? Many Thanks. Forgot new fuel filter plus air filter

[VR43000GT]

Well, at worst case senario it could be a bent valve or a worn piston ring. And it is even possible that your ECU could be damaged (but I would doubt it) which could cause this problem. As for if it has a bent valve or worn piston ring you could get that checked out with a rather simple compression test.

[Igovert500]

He already said he checked the compression and it was good.

A bad piston ring would result in blue smoke out the exhaust under load.

You are correct in your assumption, a bad MAS should trigger a CEL.

I'd start by checking your timing, not just the upper most mark, take off the belt cover and check them all.
Also pull your ECU and check for any burn marks due to leaky capacitors.

Also you may want to check for any major intake or exhaust leaks. A cracked manifold or a leaky flex section...