Time to call the nearest LPG DISTRIBUTOR the place that operates the bulk trucks and highway tankers. Folks who set residential and commercial LPG tanks.
If you're surrounded by natural gas you may have to go on a short journey.
But
These folks will know of talented Imco carburetion specialists and small engine repair shops. This is from a many times at the School of Hard Knocks experience with LPG. Don't balk at them suggesting the engine be given a compression test. LPG and valves don't get along too well.
The future savings in fuel economy alone makes this seeming hassle worth it.