Putting on a four-stroke’s exhaust isn’t difficult, but the proper way to do it is to install all the pieces loosely and then snug the bolts down starting from one end and going to the other. Some top mechanics start from the back and move forward, some like to go front to back. The key is to get everything in place loosely without any of the pieces being stressed before you go through and tighten. It’s also a very good idea to put some high temperature anti-seize or lithium grease on all junctions so you’re not dealing with pieces fused together when you go to take part of all of the exhaust off (you do re-pack your muffler when it needs it, right?). As a side note, if your bike ‘pops’ when you’re decelerating (and using the compression braking), that could indicate an exhaust leak, so if you’re hearing that popping when you should be focusing on your braking points, check the junctions of your pipe for a leak.