The one in front of the AFM on the radiator elbow.

maybe thats why i don;t know about it i have the k2rd radiator.

Yeah, it's probably only on the stock radiator.

my guess is clogged cat(s).

Check your leading coil. Make sure it's firing. If the lead coil is not working you will loose alot of power. Check your trailing coils too, take a look at your spark plugs.

i have the same issue and it was the o2 sensor......i grubbed a motec wideband and it showed me that the o2 sensor was old and tired. Remeber 13B/12A exhaust is much hotter than piston engine exhaust

my cats are laying on the floor in my garage.

FYI rx7.com has o2 sensor for like $40, i replaced mine last year.

I thought it was in open loop under WOT, that would render o2 sensor irrelevant.

mine too, but what about that performance cat u have?