My 92 5.0 engine idles rough on cold winter days and throws out a bit of black smoke. The code I retrieved was 128 (MAP sensor vacuum line broken) but the vacuum was good. I also got a code 173 (running rich) probably as a result of the MAP code. I've reset the codes and replugged the MAP sensor and all seems to be well but I wonder if these things crack in cold weather or just wear out internally or could it be an intermittent bad electrical connection due to the cold?. How much to buy a new one?