I have recently spent a few hours tuning my new 3.2SS. Build spec is 98mm mahle on SC crank (70.4mm), 10:1 CR, Twin plug, DC40 cams on 108 deg lobe, 46mm TWM ITBs with 30#/hr injectors. . I am using Megasquirt II, V2.2 with 2.888 code. My interface is an Asus EEE 901 with TunerStudio MS software. Data analysis is done with Megalog Viewer.
I found that my car idles best with approximately 13.1:1. I have found that the car does not like anything leaner than 14.5:1 at cruise. Otherwise it will have a lean surge and pop through the intake occasionally. I have WOT bins set at 13.0:1 at 95kPa and 12.8:1 at 100 kPa. I have really crisp throttle response and found that going slightly richer might feel a tad stronger but felt sluggish on throttle transition.
Here is my target AFR.
I am completely sold on tunable EFI. Being able to set target values and then achieve these through proper manipulation of fuel levels is very fun and educational. Everyone talks about the improvement going from CIS to carbs. I did that transition and it was impressive. The switch from carbs to EFI was equally enlightening.
There are a few things to look out for when tuning that might cause problems for some. For example, too large of a throttle body in an ITB setup will cause the system to go very lean off-idle due to large amounts of air that dump into the system with small throttle inputs. Swept area is very important here. The cure is abnormally high acceleration enrichment values that cause the system to bog down at higher rpm. My method was to make the low rpm, high MAP values very high in the base map. This acts like enrichment and allows fine-tuning of accel events at higher RPMs.