Next week I am getting true duals put on my 07 titan with Flowmaster 40's and straight pipe in place of the second set of cats. My question is should I get a X pipe befor the mufflers? What are the advantages or disadvantages? I contacted Flowmaster tech. support and they said not to go with true duals that it could cause computer problems and such on new trucks. I am going with true duals anyway because I havn't heard of anybody regreting it or causing them problems. They also said no x pipe, that it would make it sound like crap. Thanks.