Hello.....I currently have a HS 49cc................ SBP air cleaner........ SBP shifter kit ........My bike runs really well, but after putting on my SBP air cleaner I have had to adjust my idle screw to the point where it is almost falling out.....after setting this screw wide open the bike seems to run just fine.....quick on take off ....responds well to throttle.....and a top speed of 35 or so.....never satisfied, I read how it's possible to drill out the jet to a larger size, thinking this may add more power or at least allow me to set my idle screw in a better position.....so I tried drilling out my jet a little bigger(size 72 drill bit)....but i'm afraid I might have screw it up somehow as my bike starts and runs fine, but with a little throttle the engine starts to sound a little rough.....Haven't been for a test drive yet as we are presently over loaded with snow at the moment.....I can only assume the bike would run poorly after hearing it running rough at half throttle in my garage...Funny but it idles quite nicely.....I am wondering if this is because I need to make a exhaust upgrade?....or have I drilled my jet too big?.....Or am I better off leaving the stock jet size and have my idle screw wide open?...........Any help would be appreciated.......Can you please tell me if it is necessary to have a exhaust upgrade with a SBP air cleaner and a enlarged jet or is the exhaust optional?.....Thanking you in advance.....Rick