Why is it over heating?

So when I first got this jeep it was perfect no
complaints well one day I get an engine code
saying the thermostat wasing calling efficient
enough so I replaced it I had no problems for like
2 weeks well one day I was showing it off to my
brother and I got on it full throttle and it shot up
in the red and was overheating pulled off let it
cool down and was fine as long as I did t get on it
notlw anytime I get on it it over heats but just
regular driving it's perfectly fine I have a family
friend say the radiator could be clogged but when
it's overheating you can go to the upper rad hose
and it's tight like there's a lot of pressure behind it
that the thermostat isn't letting anything by it but
I've had friends that own the dame make and
model they say it's cause I didn't get an oem
thermostat so I'm confused can anyone help