91 sl500 surging and stalling
 

been away for awhile and still haven't fixed the top but have a good idea how.
now have a new issue. the car started to surge while driving slowly getting worse to the point it stalls and surges all the time warm and cold, scared to drive it. so far changed the fuel filter, ovp, cam shaft sensor, as well as the eha valve that was leaking, wires look good plugs a year old. used to be hard starting but starts great now. read some where that it might be the catalytic converter, if it's plugged that it causes the same symptons. the car came from japan and is a low mileage car. the air hoses all seem solid. the car ran great for 4 months after buying and i only use 93 octance fuel. any help would be greatly appreciated.
thks Bill