Not likely. I mean, you can check by doing a simple acceleration while simultaneously monitoring fuel trims. 1k, 2k, 3k RPM.
Case 1 is fuel trims improve with increase in RPM, then possibly a vacuum leak.
Case 2 is fuel trims don't really change. Vacuum leak is not likely...keep looking elsewhere.
Do you have live data or just freeze frame information? I would not say limp mode, just a severe driveability issue due to fuel trims/mis-fire, maybe both. 50% fuel trim. The ECU can't correct over 25% is what I've read. But you state A/F ratio is pretty close to stoichiometric ideal number (that's from your scanner, I assume?)...not sure what to say about that.