The seller is responsible for the smog certificate, prior to sale. If
you live in CA. here is the link.
http://www.dmv.ca.gov/pubs/vctop/vc/vc.htm

But since you have assumed title, my guess is, you are out of luck.

The stealership has told you what the problem is, now take the car to a
reputable independent MB shop, for a second, less costly opinion.

You don't tell us the state  of your residence. The terminology sounds
like it's California, also that CA law clearly states that the seller is
required to provide the buyer with a current (not older than 90 days)
SMOG certificate.

You bought the car "as is" but, though I'm not an attorney, I believe
the seller's "as is" doesn't trump CA SMOG laws. "As is" applies to the
car's condition etc. but cannot apply to the seller's legal CA
responsibility to supply the buyer with a current SMOG certificate.

The seller defrauded you by installing a third party, non-OEM, emissions
control device in violation of CA SMOG law. That leaves him open to a
suit for fraud. However, I suspect, given the seller's demonstrated
deviousness, that you'll be on your own in this mess.

Forget the dealer and find an independent shop that can bring the engine
into compliance. This won't be a cheap education.

Next time you'll first know the law and registration requirements BEFORE
passing the cash.

What part of AS IS do you not understand?

Marty

Just curious about the after market electronic device to keep the  CE light
from coming on. Never heard of such a thing. Most crooked people just take
out the bulb and try to sneak it by. Smog check stations are supposed to
verify that the light still works with ignition on engine not running. It is
my understanding that cars that cannot pass smog or have modified/missing
emission systems in California must be sold as parts only and cannot be
registered.  If the sellor is in Ca I suppose you could threaten to sue him
and see if he comes around. Small claims actions are cheap and quick. You
will have better luck if he is a registered car dealer in Ca.and turn him
in.

Good luck

Peter