Here's a curious fuel pressure condition on my 164 with D Jet. There is a fuel pressure gauge permanently installed. The electric sender is connected off a "T" fitting to the length of fuel line which runs from the fuel rail to the cold start injector.

When starting up cold, everything is fine, pressure reads 28 lbs. After warm up and then sitting for a while with engine off; say in a parking lot; on restart the pressure will read about 23-24lbs and slowly rise to 28 lbs over 3-5 minutes. Idle is fine, acceleration and running are fine. Could air be trapped somewhere in the short hose stub and give a temporary false reading? What eles might be happening?

Thanks in advance for all suggestions