Hmm, i get fps drops when looking around for some reason. I've played this game before without the GOG version a few years back and i can't remember getting these then.
Anyone with similar problems? Solutions?

Try increasing your Dosbox cycles (ctrl-F12 or in dosbox_thunder.conf). The default is 25k, but the game feels much smoother on my machine at 50k. At 75k, though, it starts to get a bit glitchy.