I have seen 145 but I have heard that it would best 180 probably 185 from some sources. I also heard from another owner they have seen 172 and that was in 5th gear at 6900rpm and climbing and they backed off.
Also what I read in some race spec info on the gt350r top speed was only 170-175 and in parentheses it said drag limited due to the R wing.
So I assume just like my viper. Less wing more speed. More wing more downforce. Just physics. More wing is good for road racing only but it looks cool as hell.