Did you check for any vacuum leaks.......?

                EGR system functional also? Starting point look at long term fuel trims at idle and extended 2000 RPM wait to see if long term goes under 10 percent preferably 5 percent at 2000 rpm. If it's close to normal then vacuum checks are in order IE: smoke the intake(cold),vacuum hoses issues,vacuum devices issues,exhaust leaks affecting O2 sensors, etc. You need a baseline for if the problem is there all the time or just under load. Just a thought Toyota never recommends changing the fuel filter in their maintenance so fuel testing is in order if problem is only under load. Yeah, it's a lot to check but remember you have the issue on both banks so keep that in mind,good luck

MAF sensor or vacuum leak.