03 Starting issues

I'm new to this site but I've been around duramax's for a few years now.I have a 03 duramax and i like it alot,but my 03 has trouble starting after it's been ran for a while starts good in the morning when its cold but I'm stumped to why it hard to start when it's warm I've been told it could be my oil pressure monitor sensor telling it not to start until it builds up pressure in the block. If you put a new fuel filter on it it starts perfect for about 15 to 20 times then goes back to the way it was.But when you get it started it runs fine has plenty of power.Where i work at we have an 03 and an 04 and nether one of them have this problem and they get started 20 times daily.If anybody has a solution or a similar problem please reply.