Just my 2 cents - when the f23T came out I followed experiences of owners rather intently as I was a K04 owner and f23T was one of the first K04 hybrids promising additional power. In short, this was (compared to K04) a very limited edition turbo and it had a high rate of failure in its first couple of years. My tuner at the time told me to stay away from them and echoed the things I was reading. K04 is a better choice, in fact after having oem K03, K04 and an EFR7163 on my car, K04 is just the best choice for these cars, it just wakes them up on the top end and reliability is sooo good as evidenced by the folks running them.