1kz-te supercustom , runs great one day then loss of power t

Please help , bought a supercustom few weeks ago , jumped in after driving it home and thought wow where did all that power go ??
Changed oil filter , diesel filter , same issue , it would seem to bog out at 3000rpm , lifted the seats and held throttle on and primed the pump on top of diesel filter and she would rev up , little bit of hesitation , jumped in about an hour later , great power is back , stopped at the shop , went to go again , turned key put foot down and loss of power again , seems to be luck of the drawer if I’m gonna get a good run or bad run , not even sure where to start , wondering if the tanks in these vans have filters and do they need the tank out to access them ?

First thing I'd check is the turbo pressure sensor (map sensor) filter. The sensor sits above the fuel pump and is fed by a black rubber vacuum hose that has a grey (or grey & white) filter the size of a small cotton reel. That and the pipe clogs with intake manifold gunk and will cause the motor to top our at 3000rpm with no real shove around 2000rpm.