Audi gauge oil temp vs MFA temp....

I have fitted a set of audi gauges to my mk1 gti. I have fitted a sandwich plate between the filter and housing which has take off points for gauges. now my problem is this:

I have just got a new 180deg sender from VW, as fitted to mk2 GTis (white top)

I have just been out in the car and the Audi gauge (take off fitted in the sandwich plate) was sat at around the first line above 60deg (any one know what temp the first unmaked line is?!?!?)

Now the MFA (take off in the normal place on the front of the oil filter housing where the take off for the stock oil cooler is, new sender from GSF) was reading NOTHING!! it finally crawled up to 50 - 55deg.

So i got home and I put the old 150deg sender that was originally on the car (i swapped as i thought seeing as how i have new sender i may as well use it….) in the sandwich plate next to the Audi gauge take off and the MFA went to 77deg!!! while the Audi one was still sat at the first line or so.

Now my question is which is right?? Are the ones in the sandwich plate over reading due to the sandwich plate being VERY hot to the touch and its heat soaking the senders, or is the original sender in a poor place (i doesnt appear to be in the full flow of oil or am i looking at this wrong? as its on the wrong side of the oil thermostat surely?!!?)

Any ideas folks?

A bit more info, while out to day around the derbyshire dales the MFA said 100deg and then Audi Gage said 130!!!!

...the sender has to match the gauge simple as that....

just fitted vdo gauges but not got oil pressure sender yet how much should i pay and how easy is wiring  also is it 12v to light ur small bulbs that fit into the back cheers in advance :wink:

wiring was easy, a brand new senders about ?30 or so so dont pay sill money for a used one.

wiring pretty easy esp if you have some of the loom from the audi, as you just match colours to colours (you will need a new temp sender dont forget) and you need a switched live that can be found on the fuse box