please can you all help me please.

When I do a heavy, dense design I loosen my tension from 4 to 3.8. H&*

Not knowing the design,stitch count or fabric used it is a shot in the dark. If it was a light weight fabric maybe try the heavy iron on and a heavy tearaway/cutaway?
More info about the item will help

When I do picture I use a heavy tear away instead of iron fusable .