I get my GTD nozzles from Smog. I doubt you'll see any improvement on a stock pump.
I suspect if you compaired fresh GTD nozzles to Fresh standard nozzles, the GTD nozzles will ding your milage slightly.
Tragically, everything is a trade off.
Just a suggestion, but befor you spring for GTD nozzles:
1.) Go 2.5" or bigger on your exhaust, from turbo to exit.
2.) Poke a hole in you exhaust manifold and install an EGT sensor, preferably from Aircraft Spruce.
3.) Remove the adjusting screw from the blow off valve. Drop a smaller screw down adjustment hole, put the adjusting screw back in and snug it down.
Leave the fuel screw alone. Turn the LDA pin incrimentally to the steeper profile until you get the performance/egt you desire. Back out the high speed throttle stop (Governor screw) and re adjust the throttle cable for more fun.
4.) install the GTD nozzles.