So I've been reading up on the P104 error.... I decided to measure the DPFE sensor voltage between the top two pins with the key on and engine off... the DPE sig read read 5V (BAD)
per http://rockledge.home.comcast.net/Ra...tage-Test.html

I run down to Autozone and connect up the plastic one ( #su2108 ~$39) and it starts running real rough. When I disconnect the electrical connector on the new DPFE, there is no difference? When I put the old part back on, same thing no difference.

Am I supposed to reset the computer by disconnecting the battery for an hour or so after putting on a new DPFE?

 

In your case, I'd definitely disconnect the battery for 10 or 15 minutes (one hour is not necessary).

 

Disconnect the negative cable... touch it to the positive cable (which is still on the battery) for ten seconds... then reconnect the negative back to the battery. That should do the trick.

Don't expect it to run perfect for a few miles, as it'll have to relearn everything.

Good luck.