Dynamat instead of carpet mat
 

Has anyone ever replaced complete 944 carpet matting with a DYNAMAT type product in the ENTIRE interior?

Yes. Very common. The car is not that loud though, and you do gain weight.
Good luck removing the hard rubbery sticky stuff. It sucks

Very, very expensive, and it doesn't really work that well. Also very heavy, as noted.

I ripped out all the old carpet, padding, and rubber/asphalt type insulation mat and replaced everything with 1/2" jute pad and lightweight felt-style carpet.

The carpet for the whole car weighs about 9 lbs, and the jute is probably another 15-20.

And the interior noise level really isn't all that different.

any pics of process?

Not really.
Just lay stuff in place and cut til it fits...

944 sound deadening is actually pretty good for the weight, IMO. If you do want to go nuts and don't mind some weight gain, do a bit of research on the best strategy for sound deadening in cars in general (it's not dynamat everything).

I removed all of mine and replaced it with Frost King duct insulation. I think it was under $50 for the whole car and weighs a lot less. Didn't notice substantial noise difference, main motivation was that my old sound deadening was moldy and waterlogged and falling apart in chunks.

LOL I did the same thing ^^^

i find these cars to be incredibly noisy. i ended up installing dynamat extreme on all outer surfaces, and dynapad on the large flat horizontal surfaces, on top of dynamat extreme. the result was an incredible improvement in stereo sound quality, and a much improved overall ride experience. total weight gain was about 50lbs. big deal.

I've noticed that a lot of restoration shops are now using the spray-on truck bed lining for sound deadening and undercoating. Sounds like a great idea to me.

I used the 75 sq.ft. box of GT-Mat, which is very similar to Dynamat, but actually thicker at 110 mil, compared to 80 mil for dynamat, and cheaper at $175, compared to $350 for the Dynamat extreme bulk pak. This 75 sq ft box did the entire car and inside the doors. I then put the stock good shape carpet back on top of it. I'm really pleased with the tightness and sound of the stereo now. I would reccomend doing it while the garage is warm....much more plyable and easy to work with.