Greetings all, I just acquired a beautiful 1980, 450SEL, 180,000 miles in great shape, when I got it (last week) it had bad timing chain slap and intake manifold leaks, I replaced the chain, tensioner and broken rail. Pulled off the intake to access and replace the doughnuts and intake gaskets, I replaced all vacuum lines in regards to the engine at the same time, it starts great, has plenty of power once you get it moving, but, off the line it will barely get out of its own way, almost like plugged exhaust, once you get it moving though it runs great. I took it to my local muffler shop and they drilled a few small holes in the exhaust system and discovered (by using a pressure gauge) that the pre-converters were 70% plugged they were sure this was the problem, I was a little skeptical as it ran great with plenty of power once you get it moving. Well, after replacing the pre-converters I still have the same problem, I have rechecked the timing and even tried advancing it too no avail, I am at a loss as to the next possibility, any one have any idea's? Thanks in advance, Phill