1 - probably not going to be your answer
2 - shouldn't need it since you have the stock exhaust
3 - should always make sure they are tight
4 - try it, people have had good and bad experiences
5 - maybe
6 - zip tie the wire so it stays open, it won't hurt your ride but it will give you a better idea of what's going on
7 - try those first, maybe dirty injectors? Maybe even a slow intake leak under pressure.
Don't try throwing new parts at it while you already have a problem, you'll just confuse yourself and those that are trying to help you.