I was wondering if this is a common upgrade for the 996 ?
it is very common with the boxster crowd. i have had an RSS one on my box. for 3 years now . gives a little boost in power and quiets the engine bay down a little also .

 

It is certainly done. Whether the work/expense is worth it or not is something only you can decide. If you have a manual it (to me) is rather pointless. I don't do it on mine because it also changes your charging and air conditioning performance. I would do it on a track-only car. However, if you like on your Boxster, you probably would on another car as well.

 

just picked up a RSS pulley but more so to have balanced with my rotating assembly since my motors is apart.

 

It's pretty common among the tuning crowd and iirc, it is the same pulley between 986 and 996. For $180 or less, it is a pretty cheap bang for buck.

I have the Mantis and never noticed any issues with charging or a/c performance. Most track people do it to underdrive their power steering so that its not overworked, first and foremost.

 

this is about the only performance upgrade left to do on my 996 . It makes 5 h.p. on a 3.2 , wondering if it will do the same on the 3.4 ?

 

I did it. It definitely quiets the engine down. No issues with charging, AC or steering. The only surprise was the need to grind down the timing boss to get the RSS pulley installed.

 

^-- what he said, but not a big deal.

 

I think the gains are subjective but that's just my opinion. Personally I would not under-drive anything as I believe the drive rotation is engineered into the unit and under-driving could cause performance issues, especially with the water pump. But that's just me.