i am running the MSD ATOMIC on my 410 in Saskatoon. (same 1500 above sea level). and its been up and down the entire time that i've been running it. Most of my problems have been vacuum leak ( high idle) but i have had the shaking . hesitation, stumbling. rough idle as well. found that the throttle blades must be barely open so the air idle speed motor can have better control.1/8 turn max. dont know if this applies to other TBI systems but this was key to getting mine to run right.
