a rich condition CAN sag power until you get into the revs enough to kinda auto balance the A/F, for lack of better words..
like, if it dumps the right amount of fuel in for a 6000rpm+ pull, but its too much for below 6Krpm, obviously it'll sag at speeds below 6K..
the best bet is to map it if possible.. at least to me.. you can buy a datalogging AEM UEGO and make a couple clandestine freeway runs and kinda ghetto map it that way. the numbers on a dyno are always a lil skewed since you're pulling a static load, it loads linearly, and you have ambient cooling (or lack thereof) to contend with, which in turn knocks off your A/F and power.. thats why dyno numbers 9 outta 10 times are calculated before you get to read them.
uh.... hmm... 31K shouldn't really be all that detrimental to anything as long as the machine was maintained.. i'm sure it's probably noisey.. sounding like an idleing diesel is one of the 7-R's proclivities anyway.
man, i wish i was more of a tuner.. i can tune, but i've never dyno tuned anything since i don't own a dyno yet.. i will, but its a year or 2 out, still..
smoke on a pull is natural. i've seen vipers, lambos and ferarris smoke on dyno pulls.. lol ESPECIALLY on uber tuned motors.. you can't really help that.. ALOT of smoke tho could be indicative of 3 things..
ring flutter, ring FAILURE, or valve seals.
flutter is 100% all-natural. EVERY motor in the world has it. it has to do with harmonics in the motor and what the ring gap is. typically, it's around 9000rpm tho, so, i'd kinda rule that out.
ting failure, well, you know you don't have that.. a good pull woulda wiped em out and you'd be fuckered.
possibility of a slight bit of blow-by on the seals.. but, that ring flutter thing is also the MAIN reason blow-by occurs, and is normally the true source of blow-by in the first place..(since its "blowing" by the rings..)
not sure what else i can tell ya man.. i'll sit her eand ponder for ya.. lol