did some research. 996 guys complain about brake feel, and 987 guys really complain about brake feel. apparently the soln is a gt3 master cylinder. did some searching and found the following:
996.355.910.00 - standard 9x6 MC
996.355.910.50 - 996 GT3/GT2/TT MC - bigger piston that stiffens pedal. expensive and only oem available (unless you want a used unit of a wrecked turbo).
997.355.910.30/TRW PMN166 - 997 GT3 MC - even bigger piston, and the trw part is much less $ than the oem part (but currently sold out everywhere).
notes:
- does not work with cars that have psm - will cel
- will bolt right up, however some variation (m10 vs 12) in brake line fitting size. soln is this:
https://www.ebay.com/itm/Brake-Line-Thread-Adapter-Male-M12-x-1-Bubble-Female-M10-x-1-Bubble/331605500736?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m1438.l2649
- other options are the boost assist; 9x7 have more than 9x6 which is why they have poorer pedal feel than our cars. gt3s have less which makes them stiffer. apparently boosters will interchange but are different dimensions (ie, gt3 unit is deeper) which means they may impact bits around them, require massaging brake lines, etc.
so, if your MC is working fine and you think you need a stiffer pedal then perhaps convert. if you MC is failing and you have to replace it, consider a GT3 unit for even better pedal feel because the increase in cost (new 986 unit vs gt3 unit) is incremental.