Curious

cuda620 sorry to here about your decision on your ride, I had a AAR Cuda the motor was on a stand and a 68 340 was in the car, standard bore .572 .296 cam, double springs, pocket work, radius valve job, & mechanical 3x2 carbs 1 7/8 hooker race headers. Street driven every day 3.91 gear and yes I had it on a car hauler to go to the track because it had 4.88 and 7"x 29 slicks. The car ran 11.80 at 115 mph, if I had a 6 speed I could have driven it to the track and got better mileage. With 3.91 I got 14 - 16 mpg and had power brakes, never had a vacuum problem that you are talking about, I have been building mopar engines for 30 years and never had the problems you are talking about, It's a uneducated engine builder that causes those problems. I have also worked for Cadillac for 10 years, GM sense 1995 so I know all about ls motors and there development.
You my friend are uneducated in the automotive world and that's just the way it is, nobody can fix you you are an idiot.