thermostat or coolant

i have an issue with my Seat Leon 1.9 TDI 2008 retaining engine temperature. I have performed an EGR delete using a blanking plate and it appears the warm up time now is now significantly slower than it was before. Once the car reaches 90 (without the heaters on,) if I'm sat idling and then...

Just changed the thermostat on my 1.6 but now temp gets up to 120 with the 3 beeps. New one went in fine, bled engine for a while and temp guage sat at 90, peaked at 95 for a few secs but went to 90 and stayed there. Kept it running, revved it to 3000 to 4000ish and topped up header tank as...