Will not start warm 2003 F115 TXRB

[finaticfishing]

Some background. Engine presented with water in oil and running rough. Found small corrosion at top of cylinder head to #1 cylinder. Ordered new complete cylinder head kit and installed.
I flushed and changed oil and filter and descaled using outboard descaler with thermostat and zincs removed using small pump to cooling water tube with lower unit removed.
started up and ran fine. After warmup, shut motor down. After a few minutes tried to restart, would not restart unless throttle advanced. Running rough and extremely rich. Soot on the ground from exhaust.
tested TPS and confirmed correct voltage at idle and increasing with advanced throttle.
IAC valve is clicking with shutdown. I even swapped the IAC valve with other motor for testing.
All cylinders have @135lbs on the compression tester, I do not have a good tester and believe the seal is not great because of the depth of the threads on the cylinder head. Unable to use the oring on the compression tester.
I let motor sit overnight. Cool down. Motor started and ran perfect. Warm up, shut down, same rough running and rich condition.
will hook up YDS when I get a chance.
Any ideas? Stumped as of now.

[99yam40]

My only thoughts.

could the motor not realize the motor has warmed up somehow and thinks it is a cold start?
make sure the temp sensors are reading properly.

does this motor have an O2 sensor?

did you put the stats back in?

[finaticfishing]

Cold start maybe.
stats are back in. New came with the new complete head.
I will hook up the yds when I getback from work travel.
that should give temps and any O2 reading if there is one.

[finaticfishing]

Here is the data from the YDS. nothing unusual and no errors. It will not start without the throttle open now at all. Plugs are black and exhaust all over the lower unit. I am going to take off the intake as a minimum and see if anything looks wrong.
This is so odd. Stumped.

[finaticfishing]

Update. Found the issue. This small vacuum T was broken behind the manifold. Goes to the fuel pressure regulator. 7 cent fix part, numerous hours of labor. Figures.

[brian3006]

Thanks for the update!! thats the way if often goes...the simplest fixes are often the hardest