B18b P75 head build question

I have a rebuilt p75 head that im prepping to set up for a 400hp turbo build. I already have BC dual springs with chromoly retainers, supertech keepers, and BC stage II turbo cams. Still plan on getting BC valves to go with it. I was just wondering if the stock diameter of our valves is sufficient enough to reach that 400hp goal or would i NEED to go bigger. If i dont have to go bigger thatll save me money from getting more head work done. And if you gotta know my compression im going for 9:1. Thanks

stock valves size are just fine for your goals. Compressed air won’t care if a valve is -/+1mm
use money on getting a bigger intake manifold… that’s where some noticable gains can be picked up.

Well I have a skunk2 mani and throttle body so I got that covered. I’ve read that people have went with just bigger exhaust valves and left the intake valves stock diameter too. Would that b a good idea to do that to have more exhaust flow. Or again just leave as is and I’ll still reach my goal of 400 with stock diameter valves? Just want to make sure I cover all my bases and options. Just don’t want to have to pay more than I have too for this 400ho build. Thanks a lot.