Low revving sound coming from trunk - Bosch 1994 Mercedes-Benz C220 2.2L Professional Preferred

You did not indicate if the key turns or not ... but regardless ... it sounds like you have a trunk latch mechanism issue and not a key lock issue ... and your remote cable from the passenger compartment to the trunk is probably broken. Not a good situation.
I am not familiar with the back seat of that car year/model ... but I would try to remove the bottom part of the rear seat to then see if there is a way to remove the top section of the seat. What you are trying to do is gain access to the trunk from the back seat ... since it sounds like your mechanism is jammed.
A low odds of success could be to take some pressure off the mechanism by pushing down on the trunk lid and then trying the key .. probably will not work but it is easy to try

the revving sound could be coming from the radiator fan clutch with the engine OFF try turning fan should have slight resistance and smooth

under the bonnet on the radiator is an automatic fan, now if the radiator is low or you need to replace the coolant in it or top it up but the car may need a service and let them know the problem.

Check the transmission fluid, it may be low.

When does is rev high and low? If it does this at idle check for a vacuum leak or maybe a blocked airflow

It sounds like it may need more than just an adjustment, the mixture screw is on the side down reasonably low close to the base plate, there are lots of different carbs used but the idle screw is usually right by the linkage point.

how do you adjust the headlight beam on a xjr1300 naked 2002 bike, is it as simple as undoing the 2 bracket bolts at the sides of the lights and re-setting the lights to a new level ??
currently it seems to be set for riding with a pillion passanger or heavy load at the rear as the lights are set low, no one flashes me even if i ride at night with full beam on !

thanks xjr cambs

did you change the filter too? If so is the new filter EXACTLY like the old one? Are you sure the trans is full of fluid? Sounds like a wrong filter or low fluid. Also is there a dent in the trans pan that could be hindering the fluid flow into the filter? If this is the case replace the pan.

usually you will get the best sound with the box mounted approximately 3" away from rear of trunk with speaker facing toward the rear of trunk if it is a single speaker enclosure you want to do the same just offset it to one side of the trunk corners always amplify sound however just so you know 10's are not really made for low bass they usually have more of a hard hitting pound instead of a low rumble usually 12's will give you the low bass better and it also depends on what kind of box a vented box would be best for low bass sealed box gives you tighter bass but you need more power ported is good for low bass but gets sloppy when loud and a bandpass is used for loud hard hitting bass

Oil pump is going/gone out