Now that's an interesting one! Park up. get the bonnet/hood open and identify whats clicking for a start.
Aircon clutch placing a load on the electrics, ECU compensates but the clutch has dropped out?
MAF sensor failing.
Camshaft position sensor / cam chain?
Just a few ideas.
I think the purge valve is fine, had a EVAP issue on another vehicle and this doesn't seem like it. I think you are on to something about the pedal or throttle as it does give a slight acceleration, but obviously I dont move because I am holding the brake down, but can clearly feel the jump and the see the RPM going up.When the EVAP System self tests run you can hear the purge valve clicking. However, that should not have a lengthy impact on the RPMS, just a short one time blip. I'll guess the pedal sensor or the throttle valve. A scan with SDS or equivalent while its happening would be revealing.
is the supercharger clicking on and off???
that will definitely change the engine load.
unplug the supercharger and see if it keeps doing it.
There is a little electrical connector just above the supercharger that you can unplug. You wont have any power, but it will still run fine and you'll be able to see if that's your problem.How do you unplug the SC?
I read something that it could be the coupler in the supercharger making the clicking noise?
There are alot of Ebay rebuild kits that include oil, gaskets, coupler, and a hand pump.