Try looking up Abner he builds gear drive, ProCharger, Fuel Injected aircraft. Kwan has his contact info. If anyone can set you straight he would be able.
X2 on Abner in Okeechobee, this is his specialty.
If it's the occasional pop, it can always be an intake leak, (timing already being mentioned). If it sounds like popcorn, it's pre-ignition / knock.
We go it with an erratic lean pop. Thought the sniper just needed to learn. 30 minutes later, we lost an engine. A year later, it’s all rebuilt and we’ve gone through everything we could think of, but we’re back to a bad tune (or appears to be).
If you are trying to tune that motor in self learning mode searching for optimum A/F ratio you are assured of running lean. Versus automotive applications, an aviation motor needs to run pretty rich under load, throw in a supercharger and call it pig rich. Your gonna want to map out the full tune yourself (or get some expert help) to keep that setup in check. Start at excessively rich and work your way towards lean versus the other direction.
Lean pop, meaning a sneeze, ok, first of all, you have to be completely positive and double check top dead center for the ignition to fire correct, next,, be sure the firing order is correct off of the coil packs to the plugs, the sniper EFI I am at a guess that it uses O-2 sensor(s) for tuning, they get very lazy quickly due to the lead in the avgas if that is what you are burning, many variables to look into.
I'm in the middle of researching this stuff for a couple of projects, the following is me rattling off what I have read, not what I have done.
The Sniper uses the Bosh LSU 4.9 O2 sensor, which does claim to be lead and Methanol compatible, the NTK unit is claimed to be more lead resistant, but at another $140. Eventually the lead will kill them all. I would definitely test the O2 sensor, Bosch supplies instructions, or just replace (keep old for spare). Make sure sensor is mounted pointing somewhat down (moisture shock) and at least 2 feet from exhaust exit (muffler included). The 2-foot minimum is to keep any air that gets sucked back into the exhaust from causing a lean reading (Might actually help your issue
Finally, I am researching multi-port systems but I'll assume the sniper is similar. I'm pretty sure you can set them up to run open loop without the O2 sensor, just using MAP, Throttle position and timing sensors. The OEM injection is still mechanical, strictly throttle position for fueling. The point is that the motor needs to run rich, there is not much point in trying to optimize A/F ratio, except to make sure it is rich but not blowing black.