Ahhh, finally got my car back. O.K. this is the update:
The guy who trained in Hong Kong also didn't know what he was doing, because I had an electrician test the circuits on the relay and it was fine. I got the car back form him still backfiring.
I then took it to another guy who fixes European carbs specifically, (he did his training in England on these Stromberg carbs) and now (after a day of adjusting) my car runs like a dream !!! It hasn't ever ran this good in the year that I've owned it.
Just FYI for anyone who owns an old 230 with one of these Stromberg carbs on it:
You can't trust 98% of mechanics when it comes to this carb. It isn't just that easy to set the mixture. Either you know it or don't, you can't fiddle with it until it works, they only make it worse.
Don't make the mistake I did, ask them specifically about the carb, read up on it, and preferably take it to someone who has worked on Triumphs or MG's, these British cars all carry Strombergs. A lot of mechanics (including Mercedes ones) claim that they know about this model ('74-76 230 )but really don't.
If you live in the Toronto area and need someone to adjust your 230, drop me a line at email@example.com and I'll give you this guy's address and number. He's good.
Thanks again for all your input.