I have a 2000 Toyota SR5 4Runner with the 3.4 L v-6 and California emissions. My check engine light is on constantly and every time I have the code cleared it comes back n within 40 miles. The code that keeps coming up is P0171, telling me that bank 1 is running lean. I took it to the dealership and they told me I needed new cats at a cost of $3,000 just for the parts. So I took it to my mechanic and had both cats replaced along with the A/F sensor and rear O2 sensor. I have gone through and replaced any vacuum hoses that looked like they may have been leaking due to deterioration, and checked the rest for any possible signs of leaks. I have also replaced the fuel filter and ran numeroous bottles of dry gas and injector cleaner through the fuel system. I have also steamed the engine through the throttle body with the cleaner and lubricator manufatured by seafoam. I have noticed a chugging when the vehicle is under load. I.e. going up a hill or acceleration from a stop. Never noticed this before the cats were replaced. I also cleaned the MAF and had my mechanic test it to assure the proper voltage, and he told me the readings were fine. I was looking over his shoulder while he was scanning it and noticed the long term fuel trim on bank 1 was -10.9%. Any suggestions or help would be greatly appriciated

Thank You in advance,
Shawn.