I am venturing a guess that the LT-20 is an older USB version that Delorme no longer manufactures as I was able to find references to it on their support website, but not much else in the way of useful information. The Delorme BT-20 works just fine and is the unit I and several other members use for their chase setup. I haven't met one person on this forum yet who was successfully able to get the Delorme LT-40 to work with GPSGate, so don't beat yourself up about it. If you can purchase a separate cheap puck (the two that were mentioned here would be just fine) you should have the problem whipped.
pdf user manual found here XL-330 for the Tom Tom XL-330 you own for the terms 'NMEA' to determine if it offers an external data stream in the NMEA format and nothing came up, so I'm of the opinion that you wouldn't be able to use that for your setup (although I could be wrong).
