Where is my LPG going?

I get about 180 to 200 on 73 ish fill up but do drive clog down in a 4.6 to be honest it is a Prinz system been on the car for 7 years so about 80 odd thousand miles and I have never had the lpg system serviced

lpg gauges are pooh....but can be improved...if a standard 0-90r then a vdo fuel gauge could be used..or get the software for your system and set the gauge up as non standard..that way you can set the 3/4 1/2 etc to be accurate..

(i get over 300= for 90l..(average driving)up to 400 if really careful..or less than 100 if booting it..4l s/c.megasquirt ecu. )