search Bowden cable adjustment.

you can take the slack out of your throttle linkages; don't change the spec, but pull in any slack.
I don't know if 380s are by cable or rod, but if you tighten the applicable part (rod or cable) you won't upshift so quickly.
Also, most Mercedes that I have had have about an inch travel in the go pedal before anything happens. Pull the slack out of the accelerator pedal linkage.
On my 116, this can be done without affecting shift linkage, on my 201, the shift linkage and accel. linkage are connected so that an adjustment of one affects the other.
Measure or mark what you do so you can get back if you get it too far out of whack.