Runs decent at idle and when you're in the throttle but as soon as you let off it starts to break up and run like crap just did a full tune up plugs wires the whole works and didn't help at all

 

1. Do you have any codes?
2. Do you have a scanner that can you read live data?
3. By "breakup" do you mean the engine misfires or stumbles?
4. Is there a difference in this behavior with just letting off the throttle vs adding braking?
5. Has there been a recent compression test?
6. What do the plugs look like?

A couple of things happen in decelleration. First the vacuum shoots way up so there may be a vacuum leak component. This can disrupt fuel delivery and the air/fuel mix. Live data will help look at this. Second, the engine rotates on the mounts. This can cause some vibration that you perceive as a misfire. It can also strain or short electrical connections if the mounts are worn.