I ran the Spearco setup for 4 years. I really liked it and went the time in my sig very untuned (black smoke everywhere) on pump gas and street tire. The problems I've seen is the small elbow adaptor at the back of the manifold and the plumbing on mine was only 2.25" which should be fine for a 12 sec or slower car. My car also would not idle with the Spearco and big turbo. It idled ok with the stocker. There's a member here who has no problems with the big turbo and Spearco that I can't explain. I had to end up moving my throttlebody from before the turbo to right before the intake man. The IC will definately get you into the 11s.
The turbomotion kit is just that, a kit and the modified stock IC coupled with the much better intake is going to give you a bigger gain.
When I first got the IC, it was my only mod other than a K&N filter. Nothing else, not even a fuel pump. I went 13.9@ 101mph at only 13psi boost, again street tire and pump gas.
The only reason I upgraded is I want to hit the 10s and I don't feel the Spearco and small plumbing would take me there.