Dave

It's even worse than that - in this car the accelerator pedal is NOT directly connected to the throttle butterfly plate. Your inputs at the gas pedal are interpreted by a computer that then directs an electric motor to actually move the throttle plate. This kind of setup greatly simplifies cruise control/idle speed correction and ASR operations but also makes diagnosis of problems very difficult unless you have access to the proper code readers and have knowledge of how to use them.

I'm wondering if there is some sort of electronic gremlin that is not permitting the throttle plate to fully open under certain operating conditions.....Maybe the professional techs could provide some insight

The TBA (also called the EA accuator - for Electronic Accelerator) is a common failure item in these engines, mine was replaced at least once.

I've never read the codes in my 400E - I do remember doing some research on what would be needed and thinking I would not bother until I actually had a problem. I'll take a look at my documentation when I get home and see what is involved with code reading.

Tim