My 98.5 had a Edge chip, with hwy mpg of 23 consistently. Then the chip was stolen during a bad experience at a bad mechanic. Five hundred miles from that mechanic I noticed the mpg dropped to 18. Bought new Edge mileage max chip and tested mpg over 600mi. now 16mpg. Spoke to Edge who confirmed that if I could note an improvement in power then the chip is working and I must not be testing the mileage correctly. In between the map sen. and the wiring harness there is a black plastic cup filled with epoxy and three wires 4in. long. With this device removed great power 16mpg. With Edge chip and this device not much power and 18mpg, as if it cancels out the Edge chip. Both Edge and my local Dodge dealer can't figure it out. Any ideas out there?

 

Sounds like it's maybe some sort of Boost Fooler. Can you post a picture of it? That may help.