Well i also ran into so many problems with my motor i wanted to blow it up but i didnt, I had a slight bigger lunati cam the 515 lift one and had plenty of vacuum. I went with an even bigger cam and still have good vacuum. I doubt cam is ur problem, i would look elsewhere, maybe distributor, are ur weights kicking back all the way? i asked everybody and they all told me different things, a little sandpaper on the posts is all i needed so they kicked back. I would get rid of the cats too, no need. What kind of carb do u have, how built is this motor of urs? i also have iron heads with small valves and can pull off some good timeslips. How did u adjust ur valves? are they too loose?, too tight? bent pushrods? What kind of intake do u have? I think everyone will want more info on ur motor. It could be lots of things, is this a stock 350 with a cam change? I really think you need to share more.