The 14cm will flow more air, lower EGT's, but be able to handle more power.
From HTT's site:
"By replacing the 12cm2 housing on your 94-2002 truck, this simple performance upgrade turbine housing will increase horsepower potential.
You can also install this housing on 1988-93 trucks BUT it will require moving the downpipe just over an inch rearward. This housing will reduce backpressure and should reduce exhaust temperatures on these trucks.
This housing WON'T fit 2000 and newer automatic transmission trucks because they use a Holset HY35 turbo and not the HX35.
Specify the application you want to use this housing on and ask us about mounting flange and oil drain gaskets. $500.00"
I also have a compressor housing used to upgrade to the 6 blade 60mm HX40 wheel. It was rubbed by the wheel a little, but is in good condition. $100 shipped.
-Dustin-