Cranks will not start

Hello, I am having trouble getting my truck to start. Truck was sitting for a while, but would start it every one to two months with no issues. However the last six months, it has not started.

Here is a list of items I have replaced/checked:

Replaced fuel pump on rear tank. I only use that tank so did not worry about the front tank pump.

Pumped out old gas, replaced fuel filter and blew out gas from the fuel check valve.

Checked fuel pressure, 40 PSI on key turn, then clicks to 35 PSI.

Checked fire to spark plugs. Good.

Checked power to injectors. Good.

Jumped OBD1, giving code 22, MAP Issue.

Changed MAP sensor.

Checked vacuum line, good.

Changed fuel pressure regulator.

I can use starting fluid to get the engine to fire, but will not stay when I stop spraying.

Checked inertia switch, not activated.

At this point I am stuck. Please let me know if there are any suggestions on how to get the truck going. Thank you.