SANJOSE2000MUSTANGGT

I recently had the intake manifold replaced, and the guy at the shop, fixed the manifold, then told me the fuel injectors were failing on one side of the block, the passenger side injectors all failed, but the driver side injectors continued to work properly. Bought 4 new ones, and 4 spark plugs (XP 103), and now it takes 4-5 cranks before engine fires. My questions is did i get hosed on the injectors?, he said it's just one of those weird things that happens when there old and taken out of the original position. Plus now the engine doesn't fire right also I looked up the XP103's and the website said that they dont even fit the 2000 Mustang GT. Please give me some in-site.

What needs to happen for the the ignition to fire correctly?
--Wrong plug