Benz e420 multiple cyl missfire

SWAP COIL LIKE FROM CYL NUMBER 1 TO 4 AND ROAD TEST UNDER LOADS IF CHANGE THE MISS TO CYL NUMBER 1 NEED A COIL OR BAD PLUG AT CYL NUMBER 4

that pertains to random secondary ignition missfire.possibbly another code to help pinpoint which cyl. is missfireing po304 #4 cyl. spark plug,boot/wire coil/or individual coil pack,ignition module.check in that order.need more info year,vin,etc.

Sounds like something in fuel system is clogged form running to low on fuel if vehicle is old and fuel filter has not been replaced for a long time.
It does not take much but a small particle to clog injector or it could be fuel pump is going out. You need to check fuel pressure and change filter and also you might have to get fuel system flushed and you might just have replace injector at worst. Hope this helps

Has the timing belt or chain ever been replaced?

because you have a bad #5 coil, and a bad plug in the number one cylinder.
Or because your wires are leaking would do it too.

OBDII those codes generally mean misfire.

P0300 multiple missfire
P0301 missfire cyl 1
P0302 missifre cyl 2
ect.

Ensure you have the proper spark plugs. Check the coil boots/wires, look for burn marks. Anything beyond that you may have to take it back to the shop.
You are misfiring on all 4 cylinders and it is not spark plugs. Those misfires if not addressed can cause serious engine and/or cat converter damage. There are lots of things that could be causing it and most of them need to be checked out at a shop - unless you want to invest several thousand dollars in the appropriate equipment and training.

a haynes manual from a parts place will show you--or chec the condition of each plug wire-if one looks bad or falls apart--probly need to get all new wires /plugs

Check your coil packs and wire's.

hi from uk i assume you have done all the above work correctly? and the leads from coils are correct firing order 1 3 4 2 ? CAMBELTtiming set correctly etc as you say this has happened since cyl head renewed and miss fire is on Nos 1+2 cyl's this normally suggest now after all work u have done and assume compressions are ok ? i had such a fault on a customers mini some years ago who had done exact type of job as you described this fault turned out to be the inlet manifold gasket had split between cyls inlet ports and resulted in missfire on 2 cyls adjoining on removal of manifold the gasket had been damaged whilst reassembling new gasket cured missfire which had caused weak mixtur on both cyls ie on induction more air being drawn via cracked gasket on each cyl and as your engine if injection same problem?? might be worth checking?? hope this throws some light on the problem?

have you changed oxygen sensors? also check wire and plug on #2 I changed plugs once and got multiple missfires changed 3 plugs to a different brand and it solved the problem