it barely moves when I give it gas

My truck was driving fine a week ago,I
park it in driveway,go inside ,come out
the next morning get in warm it up put
it reverse and won't move,put it in
driveway same thing. The only
difference I notice is that there is a lot
of grey smoke coming out of my tail
pipe. Put my side reader on her and no
codes come up. I changed out two
spark plugs and two coils and now she
barely moves in drive or reverse.
There's movement but not enough.