 2.3 hatchback heater core restrictors
hello all im still new to this forum so hope im in the right spot, anyway i am attempting my first heater core replacement on my 93 2.3 and as i was reading up on how to do it i keep reading about "flow restrictors". could someone please tell me what they are and what they do? do i need to have them in or is it a modification? i live in MI and only use they car in the summer so i could just bypass it but i wanna fix it right im already half way through it and learning alot but these "restrictors" confuse me thanks | 
