i ran one of jim mocks dev4 cams on my duel fuel ef no probs. No back firing, although it did idle lower, sometimes down to 4-500rpms when it was cold and on gas, but much better on fuel. No computer change was needed to run this cam and it improved performance heaps... but ultimatly the lpg throttle body needs to be removed if u want the full strength of the modifications. If u have an aftermarket lpg system u may be able to take the gas throttle body off wen u wanna go down the drag strip, and then put it back on for the drive home..
since then iv upgraded the cam to dev5, and removed the lpg, this cam is a bit wilder but head work has meant only premium gets used...
DEV "Street-Fighter" Headers (Extractors), Modified Cat, 2.5" Hi-Performance mandrel bent exhaust system, Hi-Flow Intake Kit, DEV5 Cam Kit,
valve train modifications, Vernier adjustable Timing Gear. "Race-Series" Head, extensive porting and head performance alterations to race standard, compression increase and Special valve springs. Unichipped