727 b&m shift install question

installed a b&m shift improver on my 727 in my 68 dart. It goes into reverse like normal, then in drive gears it engages and takes off very slowly when taking off with not much throttle, then if i gas it hard it acts as though im doing an "neutral drop" and tires turn-over really good. shifts up and down fine and does NOT bark tires between shifts if driving easy or hard. Was wondering if this is normal for a 727 to do this after intalling the b&m shift improver in the street/strip mode?

also im not driving the car untill i find out if this is ok or not so im not damaging anything just in case.

thanks