Car stalling when decelerating/tapping on gas pedal Options

[DIZNUTS]

Hello, I am new to the forum so im sorry if im posting this in the wrong place but i need help with my celica. I recently bought a 99 GT with the 5sfe engine, car needed a good tuneup so i replaced distributor, spark plus/wires, oil, timing belt, and a few hoses that looked old. Car runs way better now but im having a problem that i cant figure out whats causing it. The car idles low when in drive and feels a little shaky, almost like is choking or something but the real problem happens when i tap the pedal from a stop, the rpm goes up a little but as soon as i let off the gas, the rpm drops to the point where sometimes it'll stall. it only happens when i tap or give it little gas, like if im at a traffic jam and the car in front of me moves a little and i hit the gas slightly. otherwise it doesnt stall. i already cleaned the IAC valve and throttle body. The only code im getting right now is a p0446 evap code but i've been told that wouldnt cause my car to stall. im thinking i might've messed up the timing belt job or maybe the ecu is bad?

what do you guys recommend i check? P.S (English is my second language so sorry if i made mistakes.)