Surge with BD Plug'n' Power?

[CAT320B]

I was wondering if anyone has had a problem with the Plug n power? It seems to surge when I let off the fuel between 1500-2000 rpm. It will do it in gear or in neutral and only when between 1500-2000 rpm. It was installed 2 weeks ago and it started Friday. Any info at all would be very helpful. BTW this is my first post, sure am glad I found this place . Lots of great info.

Thanks.