Could be airflow meter, bad plug wires, the afore-mentioned sparkplugs (use Bosch Copper), check for air leaks around hoses at airflow meter, over-voltage relay fuse may have corroded terminals, fuel distributor governor, CIS temp sensor, CIS control unit, fuel pump relay... the list goes on...

Good Luck - I fought similar problems with my 190E 2.6 - had to replace the fuel distributor - only $500+

bnc