The engine may still be tight ?, I have seen this a lot, on modded cars, where starting is ok till an engine change then extra urge needed for new engine is the last straw, and slowly gives up, had it on my dads xr4i, when we changed 3.5 for 4l, as 4l was new and tight same thing.
I would first though clean up all connections, then check charge rate, do discharge test on battery, it may just need new brushes or a clean out of the starter, but as said these are famous for cooking starters.
If it was ignition it would tend to kick back when turning on starter, and pink as well once started, but only a strobe light away from fixing, if that, which I don't think it is.
tabetha