If you are converting to an old style dfi that is not controlled by a wide band o2, it might help. I am not up to date on the most recent logging capabilities of the units and the numbers can change very quickly when you are going down the road at wot and trying to watch the displays.
I have one....somedays, I think it is more gimmick than real use. It maybe that when you get your car tuned to where it runs best, you can take note of the A/Fs and maybe use them to get back to a close state of tune if you change something down the road.
I am sure you know that the old DFIs were pretty crude and known for blowing headgaskets, and sometimes worse, so I hope you have some help from an experienced user to set up the program and a dyno with a wide band monitor to help you get it nailed down without too many problems.
I would save your money and apply it toward some experienced help.
Today, the Extenders and MaxEfforts are more sophisticated than the older DFIs.
The newer ones have there own data logging programs
to record I believe. As far as being useful for a tuning aide I believe they are excellent. While driving around with various rpms, throttle positions and in stop and go traffic and gear changes the the A/F ratio numbers will move around and thats normal. At WOT the ratio will stabilize and give a good indication of your A/F ratio.
Maxeffort doesn't use the O2 sensor so I put a DIY wideband in there.
The numbers do respond fast but you need a data logger for the EGT and wideband and perhaps a good strain gauge boost gauge as well. Gonna work on that one to correlate with direct scan. Perhaps a thermocouple or two or three too.
You prolly could glance at the readings under WOT if you are one of those people that can read a 2 1/6" boost gauge while driving that way. wink
Display on mine is red easier to see at night too. Numbers are good sized.