I agree, if it's accurate and still getting the job done then just leave it alone. 790 FPS isn't that bad and besides, I'd rather have a rifle shooting 790 that's dead on accurate than a rifle shooting high 900's that can't shoot a group.... I'd just leave it........
Matter of fact I have 3 of the older version GAMO Shadows (I don't like the look of the newer ones) ,,,,, 2 of them shoot CPL's in the low 900's ........ the third one shoots CPL's around 780 ,,, but it's so accurate I don't care. I use it as a "backyard" gun. Chrony results on the gun show it to be extremely consistent with a variation of only 3-5 fps difference and like I said it's dead on accurate. The rifle has been shooting like that ever since I bought it new, I tested the breach seal and it's fine,,,, maybe it's just got a weak spring, but I don't care, I like it the way it is.....
Jeff