Dissapointing performance

I'm not an expert on setting up advance curves myself. I sent my distributor to Don at FBO and he set it up for me.
He replaced the vacuum canister and set the limits on the mechanical advance.
Mine for example is set at 16* initial and 18* at 3400 rpm. The vac canister is 14* at 14 inches of vacuum.
Do you know how he limits the amount of vacuum advance? Does he used some kind of stopper in canister arm?

edit: Sorry I misreaded your post. He putted limits on mechanical advance.