I think you are correct. I haven't installed a larger cam but I did go from 1.94 intake vales to 2.05's and 1.50 to 1.60 exhaust valves. I also increased the lift by .300. I triple checked and can find zero exhaust leaks, I recalibrated the sensor, and my hegos on both banks wander from 14.3 then creep to 14.9 then back to 14.2, repeat, repeat, repeat. My Kams show .97 to 1.02 so that looks like my Hegos info is accurate. Sucks because it just looks wrong when I look at the gauge.. IT actually gets the highest vacume reading when I richen the mix, and command 14.2 in open loop, but the wideband still shows 16.+.
1995 Cobra, 331, 2.02/1.60 fully ported GT40 heads, Extrude Honed Cobra U/L, 30# injectors, Isky Cam 228/238-524/544-112º LSA w/9º overlap, headers, O/R exhaust, 65mm t/b, 73mm C&L.
1993 Lightning, 351, AKCO MAF Conversion, Vortech S-Trim, Intercooled, 60# Injectors, HPX Slot Meter, AFR Heads, HO Mustang Roller Cam, 1.6 RR's, Longtube Headers, GT40 intake, Accufab 70mm race tb, 4.56 gears, QH, BE, Innovate LC1