Chrisk, I am new to the forum and investigating Nizpro. I have a 2008 360 with 2014 Yamaha 2 x 350 hp. My neighbor turned me onto Nixpro as his friends did the flash on their 300s (engine details I do not know) they were happy. Ft. Myers company did it. The download can be done DIY, I think but don't trust me. Like others have stated simple fuel/air modification. I have raised the question do they consider local operating conditions and regionally they have different maps? S.Fl is completely different than Boston. Additionally, I have a good friend that runs V10 Mercs on his Yellowfin, but for many years he as done this on Duramax diesels. Gives the owners a 50/75/100 hp dial on the dash board. I too only got 5400 rpm at survey, and now 5200. I cannot explain the degradation as hull is clean, engines sound/check good and only 500hrs on powerhead. Lucky me, got to purchase a new LH lower unit during covid. Latent defect in thrust bearing. Back to the point, my props are salt water series II 16.25 x 17. Lots of slip in sloppy / somewhat large waves 6-8ft, but it is all anyone can do to get this on plane in 5ft following sea. Current plan under review is buy 15.25 x 15 PowerTech 4 blade to gain rpm, and possibly the flash. I have to go HP increase first and then reprop is my understanding. PowerTech has been very helpful and more technical than I expected. They are also a Nizpro dealer. As fate would have it, my neighbors father just purchased 2014 360 Express with 3 x 300 v6. He is complaining of the same slip issue. He purchased 15.75 x 13 pitch with the goal being plane on 2 engines. Next time I see him I will ask him if they will do the flash as well. I contacted local Nizpro dealer and he said does not void warranty, i believe he is mistaken. But my 350 has the rotordynamic flaw with the flywheel. That is a pure miss on Yamaha's part. He said if you don't violate their RPM max warranty is valid. I will never run this beast WOT for any measurable distance.
Since I am new and appears 6 months behind this chat, I would love to hear if any new information is out there.