Yes, I upgraded my M3 Turbo S (not M4). There are two caps and 1 resistor that I replaced. one cap is a 6.8uf and the other a 68uf. After talking to Chris at Jupiter Audio, I went with their less expensive VT Caps and just replaced the 6.8uf cap since Chris recommended that as the biggest bang for the buck. The sound improvement was so impressive, I decided to spend the money and get the 68uf and then later after I had done that, I ordered a Path Audio resistor from the UK. HUGE improvement.
You can PM me if you want/need any more info, good luck!