CABs could certainly cause the issue you have...but the CAs might be bad also...lots more stuff you think will probably need doing and if you don't have tons of money, you should spend some of it on a professional PPI, which includes a proper subframe inspection.
In the meanwhile, you can remove underskirt and look for other oil leaks, coolant leaks, PS fluid leaks...check fluids conditions...open up trunk and look under floor mat, maybe remove a cover in the back to look at shock tower condition (and in front too).
Also, when you drive, attend to one or two things at a time...see if it tracks, if you hear bearing 'whooping' in turns, track mpgs/mph,
get codes read for free at Autozone.
There's lots you can do. But, take it to a dealer, I'm confident that they'll be able to come up with a solid $1-3,000 worth of work...which work, might translate into $500 in parts and a few weekends of your time.
You didn't say specifically, but is the car you're testing the 2001 330i? How many miles? What records, if any, do you have from seller of repair history (which, btw, a dealer could print out for you and you'd at least know what the car went through in its early days while under warranty).
Upcoming NYC dates: Jan 8 and 27. See Facebook for other shows and PM me if you can make one...love to see you there!
Mangofy your E46!