Please excuse the barrage of questions thats about to follow 
Im curious about the mods available for the Silvia. Ive been reading about two in particular -- the OPV mod for models that dont include it, and the PID mod. Roughly how much do each of these mods cost installed? Which is more useful, and indeed are they worth doing unless youre very picky? Can both be done or are there complications? Are there other worthwhile (or more useful) modifications? And finally, what possible downsides if any are there?
Phew!
Thanks in advance.

Im curious about the mods available for the Silvia. Ive been reading about two in particular -- the OPV mod for models that dont include it, and the PID mod. Roughly how much do each of these mods cost installed? Which is more useful, and indeed are they worth doing unless youre very picky? Can both be done or are there complications? Are there other worthwhile (or more useful) modifications? And finally, what possible downsides if any are there?
Phew!
Thanks in advance.

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