im making around 330awkw with a gt35.82, 20psi bp98. standard cams rebuilt head my boost has jumped a bit so could be making mayb 340kw. have u changed your valve springs mate ?
I have this issue too. Wot is perfect but light throttle or slowly building boost, especially around 4k it misfires and stutters badly. Sometimes at low rpm too. It's not vaccuum to boost transition either its on boost. Sucks when u come to a hill and all u can do is go wot.
Because 800hp and 10.3 sec means ridiculous amounts of g's. It's a common problem mate do a search. In mine with 450hp anything less than 6l it surges.
as in valve shims ? thats not possible as the shim is under the bucket and cannot leave the top of the valve, 20'' clearance for rb26 cams. plenty of gtr's around with antilag check it out, not good 4 turbos tho.