Beru & Bosch are both OE suppliers & their OE quality parts are equal!! However when Bosch supplies Spark plug wire sets in the aftermarket they supply sub-standard (to OE) quality wire & ends. Even at dealer we get these aftermarket quality wire sets from Bosch. Beru normaly sells their OE quality in sets to aftermarket. Beru make some of the finest spark plugs that you can buy, ULTRA-X. And they are copper core.
MERCEDES BENZ MASTER GUILD TECHNICIAN
ASE MASTER TECHNICIAN
27 YEARS DEALER M.B. Shopforeman
190E 2.3 ITS RACECAR
1986 190E 16V