Tripp has said what I think is one of the few true things on the internet. Back pressure to me, is when ones spine hurts. I can and have tuned many bikes with open pipes(seem to be a favorite of Harley owners). They can run smoothly ( if fuel injected) but don't make the best power, normally they are just loud. I did a guys Sprint a while back with an exhaust he made. He liked the look of it, thats fine it is his bike. It made 74hp... He said he didn't care as he wanted the look. Thats good to. About a year later he sold it becuase it was gutless and the next owner brought it back because I had wrecked the tune and made the bike slow. I got him to put the previous exhausts on and it made 122. Exhaust flow and harmonics are confused with back pressure I am sure. Back to the question, you have a bunch of sensors etc on your R3 gathering info and the ECU is then telling the injectors and ignition what to do. The ECU does not know you have fitted a different exhaust pipe and air filter, some-one needs to make adjustments to it so it can compensate for what has happened. Off to do some of that now, cheers