Carb issues

Hi guys I hope you can help me. I have been in and out my garage recently as since I have put the Vance and Hines exhaust on my bike it is eatting through spark plugs (although they seem better when I use iridium ones). I have been told that the main issue is that the petrol runs through too rich. Last time it went in for a service (February) they cleaned out the carb for me but they said there was a screw that could alter the intake to make it less rich, sorry not too up on that side of things. The problem is that the carb (and this screw) are still stock and it has seized up where they can't turn it (even with heat). They have suggested that I may need a new carb to help solve the issue so I don't have to keep buying sparks (had to put a new one in today) but this is where the issue lies. I have a K1 2001 Suzuki VL800 and I can't seem to find the carb anywhere (it has a Mikuni BDSR34). Could someone hopefully point me in the right direction or even another make/model that my bike can take. Or could there be another solution. Sorry if this doens't make sense, I am not too up on the engine and intake side of things but I can break things down if anyone needs me to. Please help me