Code #26 Check engine light

Hello again everyone on the forum, Ok here goes again, I have checked all the vac. lines great vacuum, I have purchased a new upshift delay switch over valve, which everyone said was the problem. Now instead of the light coming on every 3 day's as it did before, it now comes on everyday, since I have replaced the valve. before it used to be every 3 day's, still a code 26. Now I need real good help on this one, does anyone have any surefire way's how to repair this ugly problem. I just threw $34.00 into the trash it looks like. I can sure use everyone's head on this one. I have no place else to look or what else to look for. Help everyone, please. Plenty of vacuum at the rear of switch over valve. Thanks everyone for any and all the help you can give me. Before the snow starts flying here in Colorado again. Ben