i bought a 04 bmw 530i. the engine light came on and said running lean on bank one and two. so i checked the disa valve for a vacuum leak. and of course there was. so i pulled the disa valve and it fell all to pieces. ( luckily i got the pin out of the intake) i ordered a new disa valve and put the old one back in for the time being till the new one comes. of course i left the flap off of it. but when i take off it has a studder or skip. but not while driving at a steady rpm,. but im not getting a misfire code. any ideas? thanks for the ideas and help ahead.