I had a similar starting problem for nearly two years - long cranking time, then very rough operation for several seconds, then all was normal, but it was intermittent. Sometimes it would happen cold and sometimes warm after only sitting for an hour or two. As time went by the problem became more frequent.

I finally traced it to an internal leak in the fuel accumulator. Search for a thread started by me, "fuel accumulator failure analysis" that also describes a simple test to determine if it has an internal leak, which will not allow proper fuel pressure to build up.

Duke