rough feeling/what do you think?

I had my tranny and clutch changed and so I know the shop did a bad job of putting my H-pipe back on. From this I mean from the headers side and the cat back side. I can hear a slight exhaust leak and my h-pipe is somewhat rattling it seems. Almost as if its hitting the floor pan. So when I am driving or rev up my motor my cars seems rough. I dont know if this is because I am feeling the exhaust vibrations through the floor. But when I am cruising and not giving the car any gas and put it in nuetral and coast my car feels smooth again. What do any of you think?

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I have recently installed new solid motor mounts. I am going to swap out my of road h-pipe and put on a new high flow one with only 2 cats. Once I do that I am going to try and tighten everything up and check my hangers. Was just wondering if anyone else has possibly experienced anyhting like this?