Mine go to Falcon at Biggin, where they maintain at least five PA31s I can immediately think of, and they are very experienced in the the type (I first taxied a Chieftain into Falcon in 1985, from memory, when the current owner manager was about 4). I have been a satisfied customer with my own aircraft ever since.
I have never seen a “P” there, but I have seen loads of other pressurised twins, so I can’t imagine that makes a difference.
But, having said that, surely a TIO540 is a TIO540 and the mags will be much the same across all the many types that have them?
Your profile is empty, BB, so you aren’t going to get much response.
Is there a PA-31 experienced A&P available on this forum?
Have a magneto issue to discuss.