I definitely don't disagree with you Hotsauce, whenever I have the RX7 in for a bit of tuning, all three items are in use. But if Tone's seeing a/f ratios say in the 10's (random number), there's really no harm in leaning it out to say high 11's or low 12's at 5psi. Remember it's an SC and not a turbocharger and EGT's, unless timing is waaaaay off, won't be as hot at a turbocharged car. A really good, fast acting wideband with datalogit would work pretty well for most.

They must have changed the SAFC since I purchased it as my unit is only +/-30%. I know the new HKS unit is +/-50% but I do not know much about it otherwise.

As for the wideband link...
http://www.techedge.com.au/
Delivery took less than two weeks. You can order them pre-built or if your a sadist, you can build them yourself and save a few bucks. I use version 1.0 along with an Apexi Power FC and something called FC Datalogit (essentially turns the Power FC into something just short of a Motec). There were initial teething problems as there's no linear voltage output from the wideband and thus required a polynomial equation to create an accurate voltage to a/f ratio correlation. Wasn't super difficult, but not plug and play with my datalogit system. There was also no temp control on version 1.0 which I believe has changed with 1.5 and 2.0. They do offer a display and I believe there are third party Palm logging programs out there.

I tune by average which means each cell must have LOTS of data (which I can log). I need about 50 data points per load/rpm cell to really tune accurately. Along with EGT too. Occasionally I have access to a 5 gas analyzer on a Clayton dyno (only two in the world right now) which can really help you pinpoint if it's a fuel or ignition solution. But with the PFC, Datalogit, EGT (non logged, peak hold) and DIY wideband, I've tuned a car that's capable of 10's and daily driveable to boot.

Anyway...they're pretty powerful tuning tools, especially for the money. Not for the newbie however and I do recommend that if you have no experience, you leave the tuning to the experts. But if you do have a bit of experience and are looking to push the VX to the edge, these tools will help. Maybe Tone will be able to grab that elusive 13 second 1/4 mile time with a bit of tuning :-)