So a couple of thoughts...

First, sounds like you have learned a lesson (one burnt, twice learnt).

Second, with AFR issues it can be exceedingly difficult to troubleshoot. The old 'here's the code, replace this part' is often times a trap. When you have issues with fuel, maybe due to air leaks, issues with vanos, other causes, the DME injects too much fuel. Maybe not at all RPMSs, maybe not enoguh to trip all errors. You have two opposit codes- pre cat O2 stuck rich, post cat too lean. Odd. I've not deal with this, but maybe one bank is swamped and the other is being driven lean? I'd want to look at long term and short term fuel trims fore each bank. You may have leaky air hoses or maybe injector issues.

Third- most important- dealer GUESS at issues. Bad dealers take the codes, and simply start replacing the parts that BMW lists as 'possible issues' under the code description. They don't do any troubleshooting or test plans. And why should they? At $868 for 20 minutes of work and $200 in parts, acutally figuuring out the true issue isn't in their best interests. My point here is to NOT assume if you buy the parts you think you need (based on their second guess) you may not be successful. I cannot tell you how often people go to a dealer, get an earnest diagnosis and price/parts, decline...then replace the parts and find that wasn't it. Dealers train their SAs extensively on the "Oh, it was also something else" story.

Fourth- no shops in south Florida??

Fifth- there are three places in the US that are legendary for ripping off customers: SF Bay Area; Seattle WA; South Florida.

All I got. I'd kick the bushes here, see if someone can recommend a good shop.