Hyundai Veloster 2012 Reverse issues, acceleration issues

Hello! My car went through a bad flood, i didn't think the flood would affect my
car but it could've? Before i say anything the catalytic converter in my car was
removed by the previous owner. My car drives fine for some time and then it'll
start having acceleration issues (ill press the gas and it'll hold back, very lightly
jerk, drive substantially slower for a few seconds and then proceed to drive
normally). When this happens the D in my gear gift starts blinking on the dash,
and my car doesn't reverse unless i put it in neutral and push it back myself.
So theres two issues: the car doesn't acceleration properly, and doesn't
reverse (the D in the gear shift blinks when my car starts acting like this). It
doesn't go back to normal unless i turn it off for a few hours and turn it back
on. After about maybe 30 to 40 minutes of driving it starts doing this. Its
manageable but i really want to know whats wrong with it before i take it to get
it fixed. Please please please advise!

Kind regards,
Alex