So after a few days of work. I diagnosed my engine having a vacuum leak on the connection that goes to the brake booster. Well i got that fixed and the truck runs good now. However. If im driving and coming to a stop and take it out of gear and into neutral. The rpms stay upwards of 3k until i fully stop and it will go back to normal.

Its the 98 model 2.5l engine. 5 speed transmission
I have replaced the idle control valve. Throttle position sensor. Mass air flow sensor. Its recently had a full tune up of fuel filter fuel pump and 4 new injectors. Spark plugs and wires.

Any ideas? Im at a complete loss with this one.

 

 

The computer should hold the RPMs high until speedometer is under 5mph, that's to reduce emissions, but not 3,000rpm, 1,200-1,500rpms

Yes, +1 on the throttle plate staying open a bit, it is very hard to hold throttle plate closed against 18+ inches of vacuum, worn out spring or sticky pivot won't let throttle plate close all the way so IAC Valve doesn't have full control of idle RPMs

If it wasn't unhooked during the engine work, then unhook the battery cable for 5 minutes or so, this will clear the computers KAM(long term memory)
It will then reLearn RPM settings an throttle position sensor voltages