Hi. I�m new at the forum and I have some questions about the dna stage 2 filter. I just got the filter and with it the instructions. It says that I have to install both dna (replace stock filter) and the dna stage 2 filter "or engine damage will occur". Is that true? Kev says in the "what hp will you get" section that this is the most hp for your money. Then I wonder how do I know if the bike runs allright? Check sparkplug maybe? I only have Leo Vince and snorkel removed. /Thanx