loss of RPM.

What is your question?

recently i had a coil pack replaced due to a squirrel chewing the cables. since then i have had a re-occuring problem once the engnine reaches 190 degrees + that cause the RPM to drop when coming to and at a stop while in drive. the same thing occures when the car is shifted from drive to reverse. along with the coil pack (cylindar 1) the oil pressure sensor and oil was changed. i have a tuner that shows me the output (volts) of the oil pressure and there does seem to be a drop in volts while the RPM drops, and my oil light comes on, the only code it seems to appear is the P0521 for the oil pressure perfromance. im trying to find out if this is a mechanical or electrical failure and if there is are more options than replacing the entire harness (and if i do replace the harness, if it will fix my problem)