I have a 2003 XLT, 2.3L with 5sp that has a miss or stumble between 1500 and 2000 rpm under light throttle application and light engine load. The engine is fine under medium or heavy load and at any throttle opening larger than a fast idle. There is no CEL nor any pending codes. It is quite noticeable in 4th gear between 35 and 40 mph. I have done the following which have resulted in very little to no improvement.

-searched for vacuum leaks; replaced two hoses from IMRC solenoid to manifold and actuator
-removed intake manifold, checked for cracks or signs of leaks around manifold seals at head, none found.
-cleaned MAF, IAC and MAP sensors and throttle body.
-checked the intake manifold runner (flaps) for freedom of movement and cleaned them
-replaced plugs with Autolite double platinum
-replaced plug wires
-replaced coil pack as a shot in the dark
-replaced TPS as the original lost its spring tension although resistance values look fine with no dead spots in the POT

It looks like this issue has been discussed in several previous threads but I have not been able to find much of a conclusion. In a few cases a replacement coil pack was the solution but not for everyone and definitely not for me. Can any one provide additional guidance? TIA