With my torque converter I take off pretty fast but only do about 31mph.
With the max torque clutch ( the one that uses chain only) I have no take off but it does about 45mph.
When your running your clutch, you must have been running a (numerically) lower gear ratio. They should both be capable of simalar top speeds but the torque converter should always offer better acceleration in your kart.
I'm not sure what model converter you have but I've heard some of the higher priced/premium Comet converters offer an overdrive feature that should result in an even higher top speed potental.
Yes, count the teeth on your clutch. Then count the teeth on the sprocket you're using with your torque converter. Does the torque converter sprocket have less teeth? Then there's your answer.