I'm not 100% positive on this since I use mostly audio drum loops, but I'm pretty sure that software synths, even if routed to an audio out, do not get included in export.
When I used to use the Cakewalk session drummer (which is all MIDI), I had to go into my soundblaster mixer and tell the soundblaster to record from MIDI, then go into cakewalk and arm a track using soundblaster audio as the source. Mute every track but the MIDI drum track, hit record, let the song run through. The MIDI gets converted to an audio track, and the MIDI track can be muted.
I'm not sure how you would do this with the firepod, since it doesn't have that same sort of software mixer/router that the soundblaster had. You may need to physically route one pair of outputs to one pair of inputs with 1/4" patch cables, arm a track, mute everything but the
drum tracks, and hit record.
And who knows... there may be a better way to do this in later versions of Sonar, but in 2.2 I believe this was the only way to go. I haven't had to do this sort of midi-to-audio bounce since I started using Sonar 4 producer.
--B