When I did my vr4 first thing I've done was to see wich way I'm gonna run the pipes. Then I meassured how much of stright pipe I need and how many 45 and 90 deg bends I need. Then I start cuting and joining with tape. After all that when everything looked ok I marked the pipes with lines and got them welded at exhaust shop. It fited perfect on my car and just the way I want it.