93 Chrysler Concord 3.5ltr V6 156000 miles PCM Codes checked three times never any codes. Engine light never comes on. Car idles very rough, Surges pretty much anytime your touching the gas. Has a hard time accelerating. Once you do get to crusing speed it still surges, worst between 1500-2100rpms. I have to get up a good speed then let off the gas and coast to stop the surging. When stopping car wants to stall has stalled a few times not all the time, when stopped car has a hard time staying running the whole car will shake, does stall sometimes. I put it in netural at a long light it kinda helps but not always. Car will always crank up its just staying running it has problem with. Car sounds totaly different now almost sounds like I have a fancy loud muffler on it. Its real hard to keep running in reverse also. Its got new fuel filter, new spark plugs, wires less than 9 months ago, new air filter, new battery, ect. Ive been told timing is flucating 7 to 10 degrees ( I thought timing was suppost to flucate) Ive put a spark tester on, all cylinders had spark. Ive been everywhere nobody can figure it out. Where should I look now? What should I test to find out?