i have just had the heads reco-ed on a 380sel which was purchased for $4000 with a bad smoke problem,valve guides offcourse. I have also tuned and serviced the car for the customer and i also have a miss at idle in this car.i have narrowed it down to a bad injector in this case as it has spark and compression in the cyl but no difference when the cyl is shorted out; i have run an injector cleaner through it and advised the customer to run a few tanks of shell optimax through the car and let me know how it turns out