oil pressure ?

ever since ive had my engine rebuild oil pressure all around has be good. 40-60psi on cold startup, once it warms up it stays around 20psi, all exept when i travel a long time on highways and the engine runs a temp of about 205 its just fine when im going but when i pull of on an exit ramp and sit at the light it drop to a very low maybe 5psi. The oil has gotten extreamy thin running that the degrees for a long period of time. but once cooled down psi will bump back up to around 20 at idle. just wondering how normal this is, or what and if this is a problem. its a new oil pump im thinking just standard pump. had to mill off 0.010 of the bottom to cause the oil pan hit it. im also running 10w30 synthetic now, but i use to run 10w40 for about 4 oil changes when i was breaking it in.

btw: 351w 83 bronco
thanks

<font size=-1>[ This Message was edited by: 83broncodude on 5/12/07 10:31pm ]</font>