Motorcycle Repair: flat spot, straight pipes, chack

Question
when i bought my 99 1220C the guy had put straight pipes on it and nothing else.  Well, it had a flat spot in gears 2-5 when you really hit the gas hard.  last spring i had larger pipes installed, a K&N Forcewinder installed and requested them to rejet the carb to compensate for all.  It ran fine for the balance of last season butI took it out last weekend and it ran fine for several miles then seemed to start doing the same thing.  Is this the same problem or do you think I have a new issue?  Also, do you believe a few simple things may help me out such as a routine oil change along with new plugs?

Answer
HI BRAD
FIRST OFF GET RID OF THE LARGER PIPES. AND INSTALL A SET OF CYCLE CHACK DUELS, THIS WILL HELP THE BIKE RUN A LOT BETTER, STRIGHT PIPES KILL YOUR LOW END TORQUE AND ON A HI REVING SPORTSTER, YOU DO NOT WANT TO DO THAT, YOU WILL NEVER GET THE BIKE JETTED CORRECTLY WITH BIG DIAMETER STRIGHT EXHAUST, I DONT CARE HOW GOOD THEY LOOK OR SOUND, THEY JUST DONT WORK AT ALL FOR THE STREET, YOU HAVE THE SAME PROUBLEM.NOT A NEW ONE,  OIL CHANGES EVERY 2500 MILES AND NEW PLUGS EVERY 10K.  JOHNNY