420 SEL vs. 300 SEL

[Luntburger]

My mechanic lent me a beater 1989 300 SEL while my 420 SEL is getting the timing chain bits replaced.

Compared to the 420, the throttle is so jumpy in the 300 SEL that I nearly rear-ended the car in front of me at a traffic light in the first five minutes driving it. The gear changes come at 2,500 or 3,000 rpm in normal driving. Are all the 300s as frantic as this?

These high rpm gear changes are stressing me out.