My bike is about 15xxx miles with two brothers c2 exhaust, and stage 1 dyno jet kit in it. I Took my bike to the shop to get my carbs synched and my air and fuel mixture adjusted, in result it runs like a champ no hesitation and no poping under heavy decelerate. The next week I Installed factory pro +4 ignition advancer and Factory pro superflare v-stacks with no synch and tuning because theres no hesitation throught the whole 14k range but under deceleration it pops alittle. Then a week after I changed out my spark plugs put in new ones, the plugs that I took out are kinda blackish but not really that fouled. I Cleaned out the ram air ducks(really dirty) put everything back together, checked my vacuum lines and any other lines that they are not kinked up. Took my bike for a spin and this where the hesitation startes, in first gear taking off under normal acceleration at around 4k to 6k rpm it sputters like its spitting, First guess was my v-stack so I took it out replace it with oem stacks took it for another spin and still sputters. It all happends right after I changed out my spark plugs WTF???!?!? I need help fixing this sputtering prob and amy suggestions on what I should check for???