[Castr_85M]

I've been getting a wierd vibration between 2-3k RPM in second gear. Whether its giving the car 40-50% throttle or just driving normal the vibration is there. You can feel the vibration in the seat and the entire center console along with armrest. Feels similar like the vibration I got before when my old E34 540 had a broken guibo only that with the e34 it was in every gear, alot more violent and not specific to any rpm range and with lower gears being more noticeable.
I took the car to the dealer and according to them the tech and the shop foreman took the car for spin and blamed it on my KW sleeves, exhaust resonance, or the spacers. At the time all I had was ACM testpipes/oem xpipe/acm exhaust. If it were exhaust resonance it would have been there since i was rocking AA Race X-pipe which was louder plus I know what resonance feels like. The KW sleeves were properly installed 1st week i got the car in august by ACM. I doubt it's the spacers since the steering wheel does not shake at all and they were on 2nd week I got the car untill I got my BBS. ALLEGEDLY they checked all drivetrain parts and front suspension and according to them everything is "tight like a new M3". Needless to say, I left the dealer pissed.

I switched out exhaust to a more quieter Borla axleback. Nothing
Bent every heatshield that can come in contact with the exhaust. Nothing
Replaced the left rubber bracket that holds the exhaust because it was broken and......Nothing!
It's wierd because sometimes it is more noticeable than others. But it feels like its directly under the car. I'm getting to the point where I don't want the car anymore.
One thing I notice is that it is more noticeable the colder it is. Anyone have any ideas?
I only found 2 threads with similar problems but the members don't seem to be active on here anymore.
Sorry for the long post guys. Thanks, hope someone can help.