I have the same problem with my '02 Caravan. I've searched the internet for answers and have found nothing definitive. Like you I have replaced the Fuel filter, New plugs and wires, When I pulled the plugs I noticed one of them was wet with gas so I thought it must be a leaking injector. Fuel pressure test held at 50psi no drop. Moved suspected injector but the problem didn't move. I also replaces the ignition coil pack but that didn't fix it.
Mine also smells of fuel at idle, is sometimes hard starting (usualy starts on the third attempt) and idles very rough in gear. I did read somewhere that it might be the crank position sensor. I will try that next. It does get expensive throwing parts at it like this though. Also no codes are set.
If you find the answer please let me know!