'79 930 running rough
 

The car backfired and immediately began to run rough. Has very little power. Idles roughly at 500 RPM. It has a steady "surge" that sounds like one cylinder not firing but I pulled each plug wire from the cap with no signifigant change on any cylinder. Seems like an air/fuel issue. I looked for vacuum leak with no luck.

Is there a common weak link on a turbo when hit with a backfire?
(like the air box on a non turbo CIS)

DLG