doing a t70 turbo and all 3" piping, ordered a different intercooler bc the one i origionally had was way to big, now the one i got has 2.5" inlets/outlet , so how bad would i be effecting performance by using this instead of 3"

 

I would at the very least make the precooler pipe 2.5, or just get the 3.0 imo...

 

I made 570 all wheel hp on a mustang dyno with my talon on a 2.5inch pipe/intercooler setup. That will cover your mp70 HP range as well, you should be fine if the core is big enough.

 

Id do like Wilde said 2.5" into the intercooler and 3" out. This is how my KB cold pipes are setup but my intercooler is 3" in/out with a 2.5"-3" coupler on the pre intercooler side.

 

Alright sounds like it will work. What's the worst that will happen running it like this since I already have a bunch of 3inch piping? Higher chance of blowing couplers off?

 

Bigger couplers ought to blow off sooner because they have more surface area to push against.