I just put the timing light on the 351W. It runs very nicely at 10 degrees BTC. When I replace the vacuum line from the carburator (Edelbrock 1406), the engine just dies. It does not matter if I use ported or direct vacuum, the same thing happens. Also, I'm getting very little adjustment from the idle mixture screws. All the way in or a long way out - I get little change in how it runs. I'm stumped! Help, please. Thanks!