[wfot]

In my understanding, the ECM will "protect" the engine if certain conditions are met/not met. 2 of these are;

engine service light = on
secondary map sensor signal is not within range - it is special MAP sensor that is under the ECM tray on your's - it is different than the one attached to the back of your intake - they look the same

if any of these are triggered AND the secondaries are activated. the ECM will CUT spark/Fuel at anything above 3200ish RPM. I am assuming there are no codes/service engine light

in other words; drive it in conditions were the secondaries are inactive - you will not ever feel the shudder / mash the peddle/active the secondaries and the studder will show up. this is protect theyself design.

I had a bad studder with no codes - it was broken wires to the secondary MAP sensor and was intermittent - took 4 months to figure it out.

just a possibility from my seat in the peanut gallery

and keep in mind, you will most likely have a modified chip, that may alter many parameters - including "please ignore the secondary MAP sensor code alert"

I would call corey and start asking questions there as following the FMS may not account for any chip alterations...

John