You came to the right place with that question, my friend. His clothes are dirtier and sometimes wetter in part 4, but they are (story-wise) supposed to be the same exact clothes he has on in part 3 that he stole off the laundry line at the beginning of the movie. Green shirt and light gray pants just like Sideshow made them. The Sideshow part 4 stitching is bad though. Don't know what happened with that.
Technically, he should have the same set of clothes on from the beginning of part 3 all the way through part 8. After that, they just stopped carring about custume continuity.