1998 Dodge Caravan Rough running engine

Hello, I have a 3.3L flex-fuel engine and I have had a rough time trying to figure out why the engine is missing. It has gradually gotten worse over the last couple of months. It does it at any speed or at any RPM. I have never had an issue starting it and it never dies on me. I have changed out the spark plugs, the fuel filter, the fuel pump assembly, put injector cleaner in the tank, and had the injection system cleaned at the oil service station(not sure if this really does anything). Everything that I have done has not changed a thing in the way the engine runs. I have no codes in the system and never have the whole time. I checked the PCV valve and the MAP sensor and they both seem to be in good working order. I also checked the manifolds with a temp. Gun to check for dead cylinders and they all seem to be close in Temp. I dont think it is a single cylinder that is bad because it is not a steady miss, it is random. I have a fuel pressure gauge coming in the mail this week to check the fuel pressure, but other than that I am at a loss. I have spent over $200 in parts already and nothing has improved.