I just bought a 2001 jetta wolfsburg and I want to put in a 2.5in downpipe that will go into a 2.5in exhuast im just wondering is there anything that i will have to re-program or change with the O2 sensors that will affect the performace and will it also help to get a coldair intake or will it make it run too rich and lose performance. any help i can get with this would be great.