Hey guys thought I would just jump in on this thread too as I am having the same issue with my EL. It has been running pretty rough lately with low revs and sometimes stalling...but what worried me today was the problem that you guys have also come across.
The cars thermo fans come on, the econ light flashes and it seems to go it lhm. The car bumps up the revs and if you push it past 60 km/h it runs like s**t and feels like you are on a dirt road with the vibrations.

Would you still suggest replacing the spark plugs and giving the gear position switch a clean ??

Cheers

I definitely think I'd start with the gear selector switch - also check the loom/plugs that lead down to the transmission.

I don't think this will have anything to do with sparkplugs - its some some sort of input issue (speed, gear selection, gearbox temp) that's wrong and upsetting the ECU.

Thanks Waggin I will check these out on the weekend.