i've got a 85 380se that i love. the car's got 243,000 miles on it though. but it has a pretty decent amount of get-up and go. i don't want a race car, just alittle better gas mileage. and just a few extra hp. i was wondering if an airbox from a 560 and a new performance air filter would do anything. i also wanted to get a new exhaust system. i want a nice, european sound. it is a
v8, but i don't want it to sound like i have flowmasters on it. any suggestions, or any other little tips you guys did to squeeze a few extra hp out of these great cars? anything would help. thanks alot guys.
-brian

 

I made a few suggestions along with other listers in this thread regarding the 420 engine, all of which apply to yours since they are both M116 engines.

https://mbworld.org/forums/s-class-w126/231625-1988-420sel-upgrades.html