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LOW STATIC RPM, Engine Backfiring Background: Mooney 1963, M20E, IO 360-A-1-A with RaJay Normalizing Turbo, 4747 Total Hours, 178 SMOH, plane airworthy but bought in October 2015 to restore better than new as retirement project. 62 hours flown in 24 months since purchase while lots of down time for restoration work such as tank strip and reseal, etc. Chronology of engine problems: Aircraft has performed pretty reliably for having a period of little use for several years. Engine oil analysis at Prebuy=all in normal range, and two subsequent oil analysis the same. First engine issue was a failing left Mag due to an oil seal leak allowing oil into Mag housing (164 SMOH). Repaired and all was well. About 3 months ago, (174 SMOH) on a night takeoff, a glance at engine gauges on the start of the takeoff roll showed RPM 2300, MP 28-29”. Run-up had been normal. I exited onto taxi way, and performed another run-up which again was normal. Did a full power static run-up and only got 2300 RPM. Tried running at 2000 RPM and peak EGT for a minute in the hope that a plug was fouled. Brought RPM down to idle then slowly advanced to full throttle. RPM only 2300 RPM / MP=28. While pulling throttle back, this time the engine began to back fire a few times. Headed for hangar about a half mile away, and by the time I was half way there the engine was VIGOROUSLY backfiring at 1000 RPM. Tried to lean to reduce backfiring but had little effect. Please keep in mind, that until this moment, I had never had a problem with backfiring on this engine. A week later A/P arrived and after a day of checking various things, he felt that the problem was in the fuel system and suspected the fuel injection servo. I removed it and he took it to a repair shop that specializes in overhauling fuel system components. Full overhaul on servo, and 3 weeks later reinstalled and plane ran perfectly. Fast forward 3.7 hours (178 SMOH) spread over 3 flights. Again, a night flight. Everything normal including starting, taxi to runway, run-up Mag check, and Prop check. On take off roll 2300 RPM, 28-29” MP. This time as soon as I brought throttle back, the engine started backfiring. Tried to clear plugs by 2000 RPM leaning, but as soon as throttle reduced, backfiring begins and continues. Back to hangar, and now A/P has spent 4 days with me spending much more time than that in between his visits, doing the manual labor. All intake gaskets and seals replaced. Fuel sumps double checked for water or sediment, lines purged, screens removed and cleaned, lines removed from fuel divider and fuel pumped into measured container and timed. All 4 lines equal. Fuel pressure on electric pump alone about 10 PSI. Fuel pressure with engine pump at full throttle 25-30 range and doesn't change with or without electric pump on. Fuel Servo removed and taken for bench flow testing with no issues. Fuel divider removed, inspected by A/P, cleaned, and new diaphragm installed just because we had one. Turbo has not been engaged at all in the past 10 hours of flight. On the ground, we have moved the turbo control lever and verified that the exterior turbo lever arm is going from stop to stop. Compression checks are always in the range of 73 to 78. We have checked compression several times. A/P has rotated prop by hand and felt for proper compression feel and sound. He has inspected the valves with a bore scope and sees nothing unusual. I have asked about the Prop governor and he says the blade angle looks proper with engine off, and the prop would not cause the backfiring. He has 40+ years of experience working for several shops including a period at Purdue University and has owned his own shop for 25+ years. He says this has him stumped. My A/P is reaching out to discuss with Lycoming Engines, and a couple other A/P shops. The plane was scheduled to go into an avionics shop today for the beginning of several upgrades including an Avidyne IFD 550, but that has now been rescheduled for January at the earliest. Any thoughts on contacting SAVVY aircraft maintenance management. I know it is “after the fact” but has anyone had experience with them being able to pinpoint a problem where an experienced A/P is stumped?? BTW, I only have an original analog EGT on cylinder #3. No fancy engine monitor for help. All other crappy original Money analog engine gauges are in normal range. Ref: Major Overhaul in November 2001 at (4569 TTAF). Hours flown per year: Year Hrs 2002 22 (22 SMOH) (4591 TT) 2003 29 (51 SMOH) (4620 TT) 2004 16 (67 SMOH) (4636 TT) 2005 17 (80 SMOH) (4649 TT) 2006 7 (87 SMOH) (4656 TT) 2007 5 (92 SMOH) (4661 TT) 2008 4 (96 SMOH) (4665 TT) 2009 10 (106 SMOH) (4675 TT) 2010 2 (108 SMOH) (4677 TT) 2011 1 (109 SMOH) (4678 TT) 2012 0 (109 SMOH) (4678 TT) 2013 0 (109 SMOH) (4678 TT) 2014 0 (109 SMOH) (4678 TT) 2015 2 (111 SMOH) (4680 TT) Purchased plane in late October, 2015 2016 43 (154 SMOH) (4723 TT) 2017 24 (178 SMOH) (4747 TT) Waiting for a solution to problem Left Mag Repaired 4733 Fuel Injector Overhauled 4743 Second issue +3.7 Thanks, -mark