Originally Posted by Karlos G

Yes it was but that was on a .36/50...
To improve an engines VE as you have mentioned, headwork, cam, turbo, TB, inlet and exhaust manifolds, anything that has an effect on the way the engine takes in fresh air and then exhuasts it.

Your .48/55 will flow more at any given boost pressure than my .36/50 (it's actually the exhuast housing that changes the VE significantly in this instance), but... if for example you have a stock head then this will reduce your VE (making it harder to push the air through and raising the back pressure AKA boost pressure!) when compared to my NMS/Newman £1000 head.