Pigstiwagon ran his wrx on gas. He was doing research as he worked for a gas conversion company. I don't see the problem of running a car on gas only, tuned correctly, it would run better than being on fuel, as gas is higher ron and cleaner.

As far as I know, there are no approved conversions for wrx's so running them on gas is illegal.

Search tho, coz I'm sure pigstiwagon had a thread on it a year or 2 ago