Help !!!! My car keeps stalling

Let me start off by saying , I’ve been a long time reader this is my first posting , as I can’t seem to find much info on it .

So I just swapped a high comp 99 b20b
I used all my obd1 b18a parts

Car turns on and idles perfect

My problem is when I put it in 1st gear ,release clutch pedal and press accelerater (gas) pedal my car dies as if I’m not gonna gas

I’ve driven the car 2 weeks ago

Just now it doesn’t want to move

My car rolls if I push it so I don’t think my transmission is seized or what not

I have all new oils new clutch ect.

Recap :

Car has been driven before and drove fine
Car turns on and idles perfect
I can shift through gears with car off

Problem

Car stalls when I try to drive her
I release clutch pedal (1st gear)
Begin to press gas pedal and my motor stalls
Straight turns off

Please I need help !

I’m fiening to drive her

Any help and advice is greatly appreciated

If it’s only been doing this since the motor swap, something is put back together wrong. Re-check everything like hoses and lines.

Thanks for the help .

I shoulda been more specific
I drove my car the day I dropped to b20 in

Drove perfect

I parked it came back a week later and now it just stalls when I press the gas pedal