Is this a cam problem?

So, slant six, 198 with a super six intake and 2bbl carter carb. The PO said he upgraded the cam using a mopar purple stick. I've never confirmed any sort of cam numbers at all. Anyhow, I've tuned the hell out of the thing to try to get timing and fuel and everything just right, and it seems to run pretty well, starts well, idles well when it's warm now. No backfires or hesitations or stumbles. However, when I get on it from a slow speed (not kicking down) or from a dead stop, it really seems like it drops about 500 lbs when it hits around 2000 - 2500 rpm, and on up, like it really kicks in. Is this because the dufus put in way too big of a cam? It's not the torque converter, because he never said anything about changing the torque converter, and it breaks away from the brakes like I would expect at around 1.5-1.8K. Besides, I know what torque converter flash normally feels like, and this takes way too long to happen. Any ideas?