Toyota Repair: low power 2.4L 2rz motor on LPG, toyota hiace, valve clearances

Question
I have a 91' toyota hiace 2rz on LPG, it has lost heaps of power over the last
20,ooo ks, compressions are all around 145-150 psi. The valve clearances are
all very low (.004"-.008")or undetectible on 2 exhaust valves (tested cold), could
this be keeping the valves open a little and reducing engine power?? what
should I do???

Answer
Those two valves are the problem, there should be valve clearance of about 0.08" for the intake and about 0.11" for the exhaust, zero clearance indicates that the valves may be worn, the valves can be adjusted to the proper clearance so I would recommend doing so first.