Cathe, I have some of the same problem if I replace the walking foot with the regular foot. It seems like the stitch is somewhat larger and I can adjust it some...but not get it as big as it should be.
I'm not sure I have an adjustment for the pressure on the pressure foot...I'll check and have hubby look tomorrow. I have to cover my feed dogs with a plastic plate...so I know I have taken that off .
Thanks for the advice...hubby will have to look at it..He is very handy to have around :D