Is this a new problem or something that has occurred since the swap? Does this have full electronic throttle or the mix between cable / rod and electric?

I know the older CIS systems ( 91 300SL for example ) push the throttle back at the driver when the ASR activates, not sure about the HFM-SFI systems. 97 ME 2.0 / 2.1 systems are full electronic throttle with the accelerator pedal a pair of pots.

Are you aware of the crumbling insulation circa 92 - 95?