Thats a good question. Tuning has been difficult. I have higher compression set up thats needs to be retarded slightly to run on pump gas. I “had” a single plane M1 with mechanical secondaries (I am replacing it with a duel plane air gap now). This set up I believe is best for a 4 speed not an automatic bbody. I am planning to drop the compression at some point but thought I could improve the tuning and thus drivability by going with vacuum secondaries. I understand that moving to a vacuum secondary is not going to solve the compression issue.
