Motorcycle Repair: Misfiring Suzuki, jet sizes, suzuki gs

Question
First of all, thank you for taking the time to try to help me out.  I have a lot of experience with building recreational and racing ATV's, including boring, porting, jetting, piping,etc.  However this is the first street bike I have ever worked with.  I have a 1981 Suzuki GS 550L I recently put an aftermaket 4 in to 1 header on it as well as 4 UNI clamp on air filters. I put new factory rec. NGK spark plugs in it. I also rejetted the carbs to adjust for the increase in air flow. I have also put a new battery in it.  Since I did the mods the bike will not rev above 5000 rpm while riding down the road.  It will free rev to at least redline. I also runs fine below 5000 rpm.  I initially thought that the jetting may have been wrong and have tried an assortment of jet sizes in it and have not made a difference.  I have a clymer service manual and have tested all of the electronic equipment.  I thought that it may have been the igniter because I could not get it to test right.  I tried a good one on it and it did not make a difference.  Next I tried another set of coils on it and still no change.  All of the plugs look equal and all of the cylinders fire at an idle.  I am out of ideas.  Any help would be greatly appreciated.  
              
             Thanks
                  Chris Marti

Answer
Hi Chris,

Describe how the engine revs while riding; does rpm's pull normally up to 5k and then falls off immediately? Describe exactly what happens.

Reply to my email so I can return information files. My email addy is: mshively1@woh.rr.com

Respectfully,
Mark Shively