What you are describing is perfectly normal with a cam with that much seperation. My LE2 setup did the same exact thing. I just switched to a hotcam this year just because of the reason you are describing. I was wasting a lot of money on gas driving around 2500rpm all the time and my exhaust wasnt quite by any means, so I drew a lot of attention. I havent gotten my catback on yet so I have no idea how my car drives with the hotcam.

But I wouldnt worry about the vibration that you are explaining, it is just the way a cam that big acts. If you want something that drives better around those lower rpms get a cam that makes some more power down low and isnt so big.

 

Tis the nature of the beast. Get some gears so you can get more leverage at low rpms'.

-Dustin-