to lean?

hi fellas new here. so last year i bought a 82 kz550c from a buddy of mine. before i bought it he decided to try making a bobber harley clone but only gas as far as lowering it and cutting the mufflers off and putting straight pipes on. I never rode the bike before he modified the exhaust so i have no clue how it was stock. My problem is is that i think its running a little lean on fuel right now with no back pressure in the exhaust. im a snowmobile guy and i know that putting pipes on a sled can require changes in jetting. my question is would straight pipes on these bikes affect the jetting and make the bike run to lean? it seems to have plenty of power but seems like it should have just a bit more. the plugs when i changed them were a lighter color than what i think they should have been and it seems to take forever to warm up enough to run with the choke all the way off (5-10 min) without it bogging over half throttle or under hard acceleration. what do these run stock for jets and what do you suggest might be the problem?

thanks fellas!!!!

heres a pic of the bike and pipes if it'll help

Do you know if he re-jetted the carbs? Straight pipes will definitely make it run lean. The fix would be mufflers or rejetting the carbs. Someone who knows more about your specific model will have to weigh in to tell you what's stock.

If you don't have one already, find a shop manual for the bike. It should have that info too.

How do your plugs look? Should be tan.