I have a issue with the idle speed is High when in gear at the lights or standing still in Gear
If i go to N the idle is still high but drops in rpms ?

Also when in Drive and stopped there is a vibration that only goes awy when put in N or Park

Any idea where to start

TJ 2001 on Fact LPG 3.5

LPG mixer system could be running out of whack, when was the last time you had it tuned? I had similar issue when i had mixer LPG system, it turned out to be o2 sensor needed replacing.

Tuned ! Never , i did replace the seal and internal rubbers 12 months ago in the LPG Mixer
Is there a guide to Tuning that you know of ?

Id just take to LPG place, most will charge about $80... i never done my own tuning so sorry cant help you with that