P2097 - 2008 mini cooper clubman S keeps returning after both O2 sensors replaced help please

Question

I have a 2008 mini cooper clubman s which gets 37.5 mpg and is setting a P2097 error code after I replaced the intake air boot, MAF, both O2 sensors. Still the P2097 returns. runs great after the code is erased for 50 miles then serges and CEL turns on. I have taken it to a BMW mechanic but he thought the blow off valve was on the air cleaner. And charged me 520. $ for the MAF that did nothing to fix the code from returning.. Please help