I load 124-gr plated HP with 4.7 of Titegroup at 1.125" OAL and it is accurate, no pressure problems, burns clean, very accurate in my Sub-2000 Keltec. I did work my way up to 5.0 grains of TG but those were getting imho a bit hot.
9mm does allow +P, and without any published data for 9mm, one works up to these loads carefully especially with a powder like Titegroup.
I load the 124 grain lead RNs with 4.4 gr of Titegroup atr 1.12" oal. This is my bog standard 9mm load.
OPs load is too light. At 4.0 grains I was getting rendom fail to feed errors with the slide or bolt closing on an empty chamber with rounds in the magazine. I upped my charge to 4.2 and then 4.4 and that's now my standard 9mm load.