Oil pressure questions

[quattro2@ix.netcom.com]

I recently installed an oil pressure gauge (from a 4KS) and associated sending unit (from a CGT) 
on my 87 4KCSQ. When I start the car cold the press. pegs (5+ bar). As the car warms up the 
pressure drops to about 2 bar at idle. However, anything over 2200 rpm and the gauge pegs back at 
5 bar. Is this normal? Should there be this much fluctuation in oil pressure over the rev range?? 
Or is my pieced together oil pressure setup a little off.

BTW - Why didn't Audi put an oil pressure gauge in the 4K in the first place?!!? Seems the diff 
lock console could have been modified a bit to allow one.....

TIA

Bill