Theft recovery 2007 400 Burgman not right

Hi all! I am a newbie to the forum, also to the 400 Burgman. I once owned a 650 Burg, but it was too big and heavy to suit me. Anyway I recently traded my 1200 Yamaha Venture for an 07 400, and it is a theft recovery scoot. All the locks are jimmied and broken which doesn't concern me right now. The guy I traded with gave me a printout from a Suzuki dealer in SC saying the fuel pump was bad. I ordered a good used pump off the internet and installed it, but it still won't run well. It backfires thru the throttle body when the throttle is twisted, and the butterfly that u can see when the elbow is removed dances open and closed constantly. It even dances anytime the switch is turned on whether it is running or not. It is difficult to start, sometimes I have to stop up the venturi with my hand to get it started, and it idles very erraticly. It has very little power because of the missing and backfiring. I hope someone can point me in the right direction as to what to do, I am clueless! At least I am not scooterless, I have a Morphus 250 to ride, but when I get the Burg fixed, I am gonna try to get the wife into scooting. It only has a tick over 5,000 miles on it, all the parts look new except what the thieves broke stealing it (and a few battle scars). I will deal with that later after I see if I can get it running good. Please help me figure out what to do, I really will appreciate it very much. I live in the mountains of Western NC, near the Blue Ridge Parkway, and if it ever quits raining I am planning on doing some serious scooting! Thank all of you in advance, Jeff Boyter