My 7 FQ300 went to nearly 380 with decat, pump, 3 port, 8MR turbo and rolling road tune. This was "safe" and didn't go into the gazzilion bar boost to get there.
I was told by my tuner that to get to 400 would require cams (HKS 272 were the cams of choice back then) and I couldn't be bothered with the hassle for a few brake more that I probably wont notice anyway.
As with most upgrades you can end up chasing numbers but the thing that will give you the most gains is the mapper ;-)