I'm using this engine, Sirio 5 Port Turbo Modified. Just got it 2 days ago and already break in. High rpm at about 41000, low torque though.
Its good for those mid big tracks. No advisable for small tracks unless you run on 3 Port.
I can't tell you how much in terms of Mph but its sure faster than my previous Kyosho GSR 15 Engine.
I'm running it on my FW05RRs