I've never had it wound out on a lake but I'm pretty sure she'd make 90-95mph even with my 225lbs of blubber on her. I have no problem keeping up with my buddies on the trail, that includes a RX Warrior, a 700 XCSP, A 700 Viper, and a 700 Formula Deluxe.
I own a 1999 Formula 583 deluxe. Never had any problems with it. Max. speed is approx. 100 mph. I'll probably put precision skis on it this year. It seems to fishtail a lot under certain snow conditions.
I bought my '94 Formula Z brand new back in 1993 and I still have it today. I'm pushing over 15,000 miles and it's still running like a champ. It's my wifes sled now so it doesn't get punished as bad as when I rode it but it's still a very dependable machine. I used to bring it to radar runs when I first owned it and my best run was 103mph with 144 studs...but that was back about 8 to 9 years ago. The engine is getting a little tired so I'm lucky to get over 90mph now. It probably needs an engine rebuild but it still starts with ease and hasn't broken down on me yet (knock wood). I'm on my second track (unstudded now) and I have just replaced the skis (precisions) for the third time. Anyway, I hope that helps.
Great sled...5,000 miles and still the original track. The only thing it did was foul plugs but we cleared that up running hotter plugs. (BR8ES). Like someone else said it fishtails but thats nothing that can't be cleared up with studs.