Supposedly the Jun gears with 5 bolts are impossible to slip time where there have been some complaints with the 3 bolt gear such as the hks slipping. I have the hks and have not had a problem with them. Unless you are going to cut your cover, you wont be able to see them once installed. There are instructions on mkiv.com for the install. Tune to -4 exhaust and +1 intake. HP gained is somewhere around 15-20, plus better power throughout the rpm range.