1984 crown victoria

My fuel injected 5.0 in my cown vic loses
power as I push the throttle and when I am
slowing down going up to a stop it wants
to die. If it's in park and I rev it up as it
comes down in rpms it does. The shop
said they did a full tune up.
Plugs,wires,distributer cap,fuel filter. I'm
just going to try to figure it out. I think it's a
sensor of some sort. Anything helps thank
you.