2003 GZ250 Dies at Idle and Wont rev past Half

[farmkid4]

Hi guys I'm new here so a little info about me before I describe my problem. I am a computer tech my trade however I worked for about 2 years as a part time mechanic and went to school for machining. Know a bit about 12v car wiring etc. Carbs are something I'm not great with though and that is where I think my trouble is.

About the bike 2003 GZ250 I bought from a friend who needed the space back.
He had planned on bobbing it chopped the rear and started collecting stuff but life happened and it had been sitting for a year or 2. He had cut up the exhaust and welded some straight piping onto them. In the process one exhaust bolt got broke off so I milled that out had it welded and re-tapped it.

The airbox is removed with just a cheap pod filter on the carb now.

The bike starts up but wont idle on its own you need to give it a little throttle to keep it running. However it you try to rev the bike up it loses power sputters and dies. I can get a video clip if that would be helpful. Basically Im trying to figure out what I should do the carb seems pretty clean but Im not sure if the jets need to be changed because of the pipe/air filter or something?

whew sorry if thats a lot but I thought some of it would be helpful. Thanks for any help/ideas!