Weird VS problems

[TrustNo1]

Ok so I have both petrol and LPG and when the car is on LPG it runs fine except going up hills when it starts making a weird deep sound like the power head on a vaccuum cleaner and then suddenly it will kick into a higher gear and gain a lot of power and get up the hill. When it's on petrol it won't do that but as I'm driving along about 20 minutes later the whole car will start vibrating and it sounds like a puttering sound coming from the exhaust and it loses a lot of power and will go up to 3k revs then it will suddenly gain power and run fine then when I slow down it starts vibrating violently again then as I drive a while it will go away and be fine until the next time I run it on petrol.

[hako]

Sounds ignition related to me - I'd fit new plugs gapped to 1.0mm which is recommended for gas, check the leads and replace if old. That will be the cheapest fix. Good Luck.

[speco]

hey buddy, my vs 5ltr does nearly the same thing, if i go up a hill on gas it gets to bout 4000rpm and then vibrates and noise, but on petrol its still does it but only at bout 4800rpm and not so bad!! its driving me nuts, its got new lead an plugs, i thought it might of been starving for air or something cause it has the gas induction pieace in the airboot, so i took it out an ran it on petrol it went better but still ****in vibrates any help would be fantastic!!!!!!!