1986 BMW 325 My car loses power on the freeways combined wi

I have a 1986 BMW 325e with 221k on the clock I'm not sure if the car's doing the same thing anymore as I havent given it another freeway run since the last time it acted up. However I noticed the catalytic converter would start smelling, kinda like a mix of sulfur and metal burning. It's an acrid smell, like wet sulfur. Then usually followed by a metallic smell that came from the engine just before losing power (gas pedal pressed all the way and the car decelerates)

I've replaced the faulty fuel pumps, replace the plugs, checked the wire and cap and rotor, no evidence of blow-by (no smoking) no signs of head gasket failure (it seems) changed the oil (the stuff when this was happening was really dirty)

However the catalytic converter still makes a funny smell. Someone say it could be the timing, or the O2 sensor (yet it passes emissions!)

I may need to use this car to drive the freeway again and I do not want to get stuck.

So what could it be?