2003 seqouia sr5

[hoddymc]

I have a electrical oil pressure gauge that i added to car due to ecb board problem with stock gauge. readout of 4.5 to 75 psi but i have needle bounce at 1400 rpm to 1800 rpm and if i let off accelorator it will show 45-65 depending on heat of car. i have never had lifter noise and run synthetic 5w30 oil every 3k . help, gauge fluctuates from negative to 55 range. sending unit has been changed 3 times and my mechanic says “whats up”