People here loves such dyno queens. For a 60 lb/min turbo @ 22 psi 377 whp is not that bad. It is equal to 460-470 crank hp. It is low but acceptable with 14 deg. timing and 95 ron fuel. Don't confuse with people claims that they are producing 500 whp with 1.5xtr or 18G turbo. Its an American dream.
You may spot on spool. It should spool around 4500 rpm without and 4000 with AVCS. Spool is where you achieve 1 bar of boost. It is not full boost. You may expect full boost 300-400 rpm later on that.
You have a high injector duty cycle there for a petrol based fuel so you may be looking for new fuel pump like Walbro 450. Your injectors will fail to feed that turbo if you switch to alcohol based fuels. So be worth checking new a set of 1300 or 2000cc if your aim is to achieve 530-540+ whp.(most out of your turbo)
You would struggle to get more power from a GTX3076R with that fuel. If you are in PRC why not use M85 instead of 95 RON! You will get most out of it.