IMO you actaully wet a carpet more with lower psi. With 200 - 250 psi, I find that one wet pass is all I need to get that area of carpet clean, especially since I use f90 in the tank.
Where as with lower psi you tend to go over an area a few times for teh same result.
You'll still get great rsults with 130psi. Just make sure you spend the extra time pre-spraying, agitating and spotting.
I think steampro's from prochem go as low as 100 - 120psi.