First of all thanks to all the members who have helped me with my past inquiries. Thanks to you I´ve solved most of those issues. My current problem is that it takes way too long for the water temp to rise to N. Usually that shouldn´t be a problem, except for the fact that If it hasn´t reached N, when I press the gas (faster than regular running. Like when needed to pass another car), engine stalls so I have to gradually give it gas to raise revs. It takes about 25-30 munites to Reach N. Could this be a thermostat problem?

 

That's about all it could be. Unlike over heating, under-heating doesn't have too many causes. When i went to "replace" my thermostats, i found that there were none there. So just a heads up. Previous owners might do strange things to counter act overheating that doesn't address the real problem.

 

stats are stuck open or not there. This will not "overcool". It will take longer than usually to come up to temp which is BAD for the engine. Then it will go on to overheat. If they are stuck open it won't overheat but act as usual and take forever to heat up. If they aren't there at all it will overheat.
The coolant moves so fast it doesn't stay in the radiator long enough to cool and not enough heat is transferring to the outside air.

replace the stats with jaguar genuine and see where you are after that. If it does the same, my bets are on the gauge itself. Buy a cheapo IR thermometer gun and verify temps yourself

does the stalling issue disappear after it is up to temp?