95GT Need a little help

Greetings. Have just purchased a keyless entry system (OEM) for my 95GT. Need info on installation. Anyone added factory keyless entry. Also having a little idle issue. after highway runs 70 to 80mph sometimes engine wants to idle at 1500 to 2000 rpms. If I cut off the switch and restart it idles at 650rpm. Occurs days apart. Temp, oil, everything normal.