The rifle cleaner was to large? What is Dowling? Do you have the same heat exchanger as the 600sci?

I think it was like 3/16 dowel. Mine was a 502 so it may be smaller, dunno.
did your flow issue happen slowly over time or come on fairly sudden

oops, I read what size dowel. Its wood turned. Think tiny closet rod.

It came on very sudden. Been trying to find it ever since. Also i don't know what a dowel is

Its possible the suction line is bad and collapsing internally.
I edited my last post , but dowel is just wooden roundstock, available at any craft store and most hardware stores.

I got a rifle cleaner kit. Im going to give it a shot. Ill go from there I guess. This is my nightmare

Was just reminded of another person with similar issue, turned out to be a clamp not fully seated or tightened allowing air to be drawn in as demand increased.
Having strainers l have to believe your issue is on the supply side of the pump somewhere if no impellers have grenaded in there.

Did anyone mention to check the water psi sender also ? They are in a brutal environment as they do not get filtered liquid like an oil psi sender does and they of same exact design and can go bad (plugged) easily.

How did the rifle kit go?

No answer here on my above post. I can definitively tell you that I have seen water pressure issues on more than one Baja with their fresh water flush system getting gummed up.

I cleaned out the heat Exchanger last night with the rifle cleaner. Nothing really came out. I also flushed water straight through, and water seamed to come out of every hole. No dice..

Still have to keep looking

Replaced all the gaskets i could see. Still searching for the issue