I tryed also LM324 amplifier (have some expensive sensor MS 5407 and I mean i found something equal and very cheap for experiments), but resolution is not the problem now. If datasheet say 80mV so the difference must be about 80mV by maximum pressure not 2,5V constant without any dependence on pressure... (with 3V power is 1,5V constant ... this mean half power voltage like dividing resistance....)....