L67 tuning with A2A and MAF?

[VX L67 Getrag]

OK have been tuning this beast now for a couple of weeks trying varying methods & parts & have got it pretty right with everything in stock positions except for the hardest thing possible....

TIP-IN, the transient when you touch the throttle causes instantaneous rich & then lean & finally catches up, I've tried removing every aspect of Accel enrichment but it still has the richness before lean & causes a delay for 0.5 seconds, can anyone see another way around this without moving the maf to the cold air side?