westcost,
the 4G93P inlet manifold has the same 54mm inlet as the GSR, but it also has a runner for the EGR system and has smaller runner outlets (~2mm smaller) than the GSR. for me, i had purchased my intake manifold and head from separate parties so it was RM150 for the inlet manifold and RM500 for the head (non-RS head). anyway, if you wanna port the manifold yourself, you're looking to spend at least RM200-RM300 to buy the tools. i already have most of the tools so to speed things up, i needed to purchase a RM22 rapid cut carbide burr. took me about 2 hrs to grind it to a rough 60mm diameter and then sand it down to 60mm (+/- 0.05mm). so it's actually quite cheap to do it all yourself, but if you've no confidence, i'd suggest you look for a machine shop or a buddy that's willing to do it for you, you're looking around the same if not less from the figures i mentioned earlier to get someone else to do it for you. but where's the fun in that! :D