boost is great so long as the engine can withstand it, if your engine hasn't been built perhaps it can't; least not for very long lol. Sounds like you're getting into detonation @ 20+ psi and the timing is kicking back to compensate. I'm a big fan of water injection (Aquamist), rising rate fuel pressure regulators (adjustable w/ gauge) and/or larger injectors. That should learn it...lol

FWIW: I've run 18-20 psi boost before in my old SAAB and always noted the gauges (boost and egt) both go up and down and up and down like a roller-coaster. After resolving the fuel issue w/larger injectors, RRFPR, and Aquamist though, everytime I nailed it, it flew straight to 22 psi in all gears and stayed planted; very fun..

Then the clutch started slipping and well...you know I was kinda back to square one lol.

Phil

03' allroad Atlas Grey; Body Clad painted 03' Nissan Maxima Grey, Smoked tail lights, Neuspeed Chip, K&N Filter, H-Sports (hard), Mufflers removed (straight pipe), Mandrus Regenmeister Rims: 19x8.5 w/25mm offset on Pirelli 245/45-19" Tires, 20% window tint.

06' Kawasaki ZX-14 (Busa Killa)