HELP PLEASE running lean under boost

[ep31lover]

Ok here is the run down. RHD converted and silvia front end. the car is running nistune for the ecu. The fuel is DW 300 pump with new filter and 700cc red color top inj dont know brand. It is running a greddy td0620G turbo kit and 19 lbs of boost. electronics changed New ignitor New coil paks new spark plugs new maf sensor. The pump has a new hot lead and is run off a heavy duty swith at 14 volts. Now the car was tuned in green bay and it ran and pulled great for 75 miles. After getting home it started to break up and run super lean at high boost causing it to pop and backfire. (this is what i took it to green bay to fix this problem ) anyways after looking into it more i rewired and soldered the injector harness ends. and replaced the fuel filter. When the car is cold it runs 100% perfect but once it gets hot you can watch the wideband and the egt go up. The car is always at 12.1-12.3 on the wideband but once it is warm the gauge can see 16-17 at times under wot also egt goes over 12,000 but yes when cold great when warm sucks i have tried unpluging the o2 sensor and its 100% the same. I have not taken a fuel pressure reading because i just dont think that it runs out of feul when hot ??? please feel free to ask me any questions other then the welding and the tuning i did it all please help thanks again