Temp sensor question

[RB92GT]

A few days ago I installed a new 180 degree thermostat and a chrome thermostat housing. The new t-stat housing has a port for a temp sensor so that I can install an autometer mechanical temp gauge and still have my stock p.o.s. gauge in the dash working (having a dead gauge would drive me nuts!) My plan is to install the autometer temp sensor in the place of the stock temp sensor and put the stock temp sensor in the thermostat housing. Well, I purchased a new temp sensor and put it in the chrome t-stat housing (using thread tape on the threads) and extended the wire which connects to the stock sensor so I could connect it to the new sensor. Ok, the point is the new sensor in the t-stat housing reads much hotter (guestimate= 20 degrees hotter) than the stock sensor in the lower intake. Any ideas why the two temp sensor locations are reading such different temps? Right now I'm still waiting for the A-pillar gauge pod which is on back order from summit, so I haven't installed my autometer gauge yet. The reason I just purchased a new temp sensor is so the old one will plug the hole in the lower intake until I install the autometer gauge. Sorry for being so long winded!

Thanks everyone,
Ryan