My 05 X-runner has been running ridiculously lean at WOT for some time. I replaced the fuel pump at a little over 200K miles with the Walbro kit from URD. This seemed to help a little but the truck still runs lean. To give some history, before changing the pump, the truck would lean so hard that it would sputter and backfire / cough when trying to accelerate. It has very few mods (long tube headers, gutted cats, old TRD intake and now the urd pump). when I monitor the OBD2 readings on my Torque app, it shows full lean at WOT (like 17.0 or worse). cruising it stays around 14.7, but under light acceleration, the fuel trims are always high (in the 20's). The motor was exchanged for a motor out of a 4wd 4runner back when the truck had 127K miles (original motor got rod knock). The new motor never seemed quite as powerful as the original, but it has progressively become worse over the years. The Walbro pump makes good pressure (tested at 50 psi with the low speed resistor on and around 55 or so with the resistor off). Could this be just bad injectors, or maybe a bad maf, or does the 4runner use different injectors from the xrunner all together? I tried searching for "lean" conditions to see if someone else has had this same issue, but I couldn't find anything comparable. what can I do to fix this issue? MAF calibrator? New injectors? cam control solenoid replacement (drawing at straws here). Any advice?