Anyone had experience with this?
Pilot flying our IVP (TSIO550E3B with 4 blade MT) and reports:
"Had backfires(?) couple of nights back. Was running lean of peak with  
temps 1590 at FL150, around -15C, light rain,  29Hg 2500rpm .
Happened twice so went rich of peak for remainder of flight with no  
problems. Any reason come to mind?"
Be grateful for any thoughts

Phil Sexton
Melbourne