I am ready to buy a used 35' Fastec w/new 496MagHOs
Any ideas on the dbs and if it is a good system??

There was a great article in the latest issue of Hot Boat Magazine on mufflers. In water tests on a number of boats. It seems from the article it does not take much to quiet down the 496's.

you'll be fine. my 454 mags are far from loud especially when sitting still, the flaps on my silent thuder are almsot under water.

I have Eddie marine switchable mufflers on my H.O. and got stopped for a DB check on lake George over the summer,, was reading between 98 and 102 with the mufflers on,, had they been off I would have most definitely received a 250.00 noise fine.

I have the same boat/engines. Quiet as a churchmouse at idle...you'll get no hassles.