The number isn't significant if you are only doing it for a number bro. If you dyno with the 16's to get a higher dyno, then put the 18's back on, what's the point ?? Bragging rights.
I had to learn the hard way man. My driveline is pretty dyno friendly. Reduced parasitic loss via ud pully, and ewp. Carbon fiber drive shaft, M6, 3.42 gear in a built DTE stg III with all the bells and whistles, also an Exedy twin plate. Great dyno numbers, but didn't ET to well at the track due to poor 60 times (driver mod needed) Did however trap 123.6 mph into a stout headwind, so that gives you a bit of an idea of her potential. A4 guys with h/c etc etc, big stall, and gears always dog my times. With numbers like that why aren't you in the 10's ?? LOL. With all that rambling, numbers are just numbers. Good luck on getting the numbers you are looking for.