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You could have a bad pulley on one of your accessories. I remember that there are 2 different pulleys for the alternator. One is a little bit larger. Sadly, when they are replaced, part number refer to the alternator, not his pulley. The SHO alternator was shared with the Windstar which have a bit larger pulley IIRC. It could be also the pulley of your new pump maybe (but I don't know variants for this pump).
Also, check your tensionner if its moving freely. Mine was stuck in open position because they are at a very low level and lot of dirt entered in it. My mechenic spray a lot lubricant in it and make it move on and off many time until dirt came out. Dirt could makes your not opening correctly.