This could be a couple things but we need to start with what it does when it does not start.
I assume it just cranks but what happens if you hold your foot to the floor and then crank the engine? This is called a clear flood start so it will cut the fuel and if the engine starts then we do have an over fueling issue.
Below is a diagram of the central multiport fuel injector (CMFI) which is what I assume you replaced? Then when you say it has a mod on the distributor, what exactly would that be?
Have you removed the spark plugs and look to see what they look like?
Below is a also, a chart that will help with this. Let us know what questions you have and what you find. Thanks
Images (Click to enlarge)
Monday, May 17th, 2021 AT 6:36 PM