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.)

[Box]

I'd double check the timing, as well as making sure the crank and cam sensors are kosher. There's also a test for the IACV to make sure it's working properly, sometimes just cleaning them isn't enough and odds are that gasket has long perished by now so if that wasn't replaced it could be leaking.

I'd double check the IACV first though as it's easiest.