If the MAF cal is not spot on you may notice such weird situations in lower gears where the load and RPM ramp faster which means there's also less time for corrections. Also, even with upgraded internals below like 4000rpm such lean sports are not unseen if you shoot for high load (and also reach it) in the lower gears if you don't have some sort of aux fuelling that can also react to some input (boost usualy).
So what intake do you have? Maybe I have a good MAF cal for it somewhere in the dozens of tunes I made for various people...