I replaced that valve last year - no difference.  But problem is solved.  I bypassed the relief valve and it now goes up like it should.  In the end it was obvious it was the relief valve once we confirmed the pressure output of the tractor.  I assume the valve is just there to minimize the load on the lift hydraulics.  But that is the only implement I have that has one and I did check and the hydraulic cylinders are rated for 3000 psi and, of course, the hoses are rated for more.  So now I am debating whether or not to get an adjustable valve.  For whatever reason I think it just takes a bit more than 1300 psi to raise it.  With an adjustable valve I could set it for a pressure just above what it takes to lift it.

Thanks