[scary driving]

Ok, so you had me looking at maps to find out where in Brasil you are located (I only know the obvious places, since I have friends and family over there), until I figured out ruralis is rural in portugués! I know that Florianopolis has some of the hottest women on the planet, which is need to know stuff! Anyway, no disrespect meant. Here where I live, I know of 3 people who are somewhat versed on porsches, and I don't trust any of them. Lucky for me, I'm not illiterate on the subject. The particularities of back pressure, I don't know HOW it will affect YOUR engine, but I can tell you this: You guys have mercedes benz torinos over there, so you'll know what I'm talking about. I had a case whith a 904 engined one just 2 months ago in our fleet in which the muffler became clogged with sooth after it blew a turbo. It would run fine, and after about 30 to 40 minutes it would start losing oil pressure and idle rough. Of course, the engine would shut down due to the safety programming on the ecu when it went below threshold oil pressure, but you get my point. It took us a while to figure it out. In most cases it will not be obvious. You can get lucky and it "just" overheats, or in a very extreme case, it wears your valve guides, or as is the case with jaguar v12s, it drops a valve seat, which is common on those engines when they overheat. I know engines in general, not porsche engines in particular, if you know what I mean.

The absorbing material is usually some kind of steel wool type of stuff, but again, someone who works with mufflers and is willing to take a crack at it might even recycle the material from other old mufflers. The reason for suggesting a tig welder is that it will create minimum deformation and will look presentable. Other than that, it's just a case of open it up, add absorbing material and weld it back closed.

P.S.: Which part of Brasil are you at?