Don't know how is situation now, just saying what he himself said. Last time I was watching him at Black Rock masters two years ago when he won it. Average was around 200kmh . Few ones were 220+ and how his record from playing days was 225 he was there.
But regardless to speed perception that in mixture of eras guys from '90 would lack from this era is wrong. Give '90 guys today's surfaces and this era guys racket technology from '90 and i think it's obvious who would be harmed more.
Racket technology has not improved in the longest time. The best players' rackets today are still widely considered as the PC600, Pro staff moulds, POG etc. Players use paint jobs and those with a keen eye can spot them from a mile away. String technology improved vastly in the late 90's with the likes of Luxilon developing etc but still, there's no better all-round string than gut.
Goran loved playing with gut and used Babolat All Season pretty much throughout his career. There's no way that today he's going to jump to some synthetic like Big Banger, RPM Blast or whatever. Considering he's 41, had umpteen shoulder problems and no longer has close to the power in his legs as a result of his age tells me that he's either being fooled by tampered speed guns or he's just trying to be smart. I've lost count at the amount of times I've seen past pros bombing down serves at exhibitions and on the Blackrock tour that look barely 115mph and they're registering 125mph+.