whats up guys, this is my first post and need a little advice.
i have an 88 s15 jimmy with a modded 2.8 with edelbrock headers with y-pipe but this system is for the carb 2.8.

what i need to no is this is listed as a 2-1/4 system does that mean thats the inside dia. of the y-pipe end??

im asking this becouse as i sead it is now on a 88 2.8 with tbi and this truck came with 2-1/2 exaust.

so i need to adapt the 2-1/4 to 2-1/2 and need to no if they mean inside dia. thanks.