AFR slowly richens at idle

When you run big cams with low comp you don't actually compress much of a mixture at idle. You actually need to be rich at idle to sustain the load. Your cam has much more than 45 degrees of overlap so you bleed off a lot of cylinder pressure which doesn't help. When you run 34 degrees locked timing you need to have the mixture lean to work as lean mixtures burn slow. Try lowering the timing and richen the mixture and try and get the idle rpm to drop as little as possible when you go from park to drive.