ok found out the 1 pixel border export in pyxel is different from what corona expects. corona seems to expect a 2 pixel border when you say 1 pixel. because it takes a 1 pixel border around every tile, so 2 tiles next to each other both have a 1 pixel border therefor there are 2 pixels in between them.
whereas the export from pyxel only puts 1 pixel between both. dont know what the best way to fix this would be. can edit sourcefile manually but is a pain. hopefully there is a way to do it in code
i could also create a photoshop batchscript change the sourcefile. which i d run everytime i export. that might be easiest