im having trouble installing a vance and hines exhaust i just got from bike bandit.....my bike ran great with out it, and now i rejetted the carbs to 150 mains 40 pilots......bike is a 1993, i dont think the pipes are sealing with the engine because it is back firing inbetween the engine and the headers........also how has everyone mounted the exhaust? It wont work with the stock hanger?

as for it backfiring between the engine and the headers did you get new gaskets to put in there cause i had the same problem when i first installed my new exhaust.  Once you replace the gaskets you should be able to get a better seal.  They are crush gaskets as i understand and noticed that when i got the new ones and compared them to the old ones the new ones were definitely thicker and created a nice seal.  As for using the stock bracket i dunno since i went with the jardine system and it came with its own mounting brackets that worked perfectly.

150 and 40 is for K&N lunch box and pipe - you should be running those ... then make sure your floats are right too ...
Cool.
Buddha.

ok i ordered the new seals, but just forgot to use them, so i put them on and the popping is gone.....now i have a huge flat spot around 5k to 7k? I am running the lunchbox filter. im using 150mains 40pilots 1 washer and 3 turns out.....any suggestions....it ran fine before i did this?

Sounds like you are at the same point i am now where it is just tweaking the carbs a little bit to get them just right.  I have been looking at the plugs and seeing if i need to go leaner or richer and keep making adjustments accordingly.  Seems like a never ending battle but will get there eventually.  I hope.