What sort of FTE problems? Are the cases stove piping sideways or getting kicked upwards into the charging handle area?
If you've got weak ejection (stove piping sideways), I would first check the fit of the extractor and its ability to hold empties snugly against the bolt face.
If rounds are being kicked upwards, I would look for shell cases contacting the mag lips.
After you've checked the extractor, your next bet would be to continue experimenting with the recoil and hammer springs.