Could this lag (not due to the turbo lag) be solved with ITB's since we're talking about a totally custom intake? They wouldn't be cheap, but they would reduce the intake runner length tremendously. This lag is caused by the elongated distance between the TB and the valves, so when you step on the gas and open the throttle, it will take that air a while to travel the 26" to the head. With the ITB's in place, this length for the air to travel would be reduced.
Referring back to the original post, why can you just run an angled spacer? Just thinking aloud here; but one like this off Ebay:
http://www.ebay.com/itm/T4-TO-T3-TURBO-FLANGE-ADAPTER-W-ANGLE-CA18DET-KA24DET-180SX-RB25DETT-R32-/200833291856?pt=Motors_Car_Truck_Parts_Accessories&hash=item2ec298d650&vxp=mtr
Granted, it is a T3 to T4, but you could cut off the T4 flange and put on a T3 flange or whatever flange turbo you are running.
But I'm not sure the clearances with the framerail and steering and such would be.