car was bubbling!!

so we decided to take the coupe for a little drive today... as always, except i didn't get on it as much as i usually do.
so some background info...
i was driving the coupe on my bday june 23rd yeah remember that day it was like 101 degrees... well i didnt have a hood on it due to the fact the hood didnt fit cuz the motor is gigantic... so the coolant siteglass (made of plastic) broke... not sure if it was too hot or a rock or something hit it and broke it.... got it towed home. ((car never overheated))
bought a water temp gauge because we weren't sure if the stock 240sx gauge was working... car has been heating up to 210 to 220 was the highest it was. so whenever it got that high, id pull over and take a break. always worked....
then today we decided to drive around the block and see if it climbd anymore, it did MAYBE one degress... but when we got back to nick's... we heard the coolant bubbling... plus i put water wetter in the coolant.. you would think that would help..
i think it runs hot cuz 1. its got 550cc injectors instead of 440cc and we haven't tuned it, and 2. its only running on 7-8psi when stock ecu is used to 12psi...
so hopefully thats all and when it gets tuned and all the tweeks fixed... itll be fine.
plus i ordered 1inch hood spacers ((ik it looks gay but if it prevents my car from overheating im all for it))
goodnight!