I have HKS filters and 3" 5zigen catback. That 5zigen muffler is not straight through. it has 3 sections and 3 pipes inside. It's very quiet. exhaust goes to the back of the muffler then returns in front and goes to the back again then into atmosphere. intercooler is stock but i'm upgrading it with bigger smic. downpipe is stock too (JDM catless i guess) but i'm thinking of upgrading it too. so can i remove my cat safely withought porting the wastegate?

 

There is no magic equation for getting boost creep. Some cars get it, some don't. If you want to add a midpipe, you'll just have to see if you get boost creep or not. If you do, then you'll need to figure out which way to deal with it.

 

how much whp can i gain aproximately by puting a midpipe? somewhere under 15 i guess

 

i would say well under 10. the exhaust sounds a bit odd.... is it heavy?

 

You could always try a setup with full open intake and exhaust without porting your wastegate.. and if you pop your motor then I guess you'll know

 

I wouldnt take the chance wait until you until you can port your wastegate. The midpipe really doesnt give you that much horsepower to make it worth taking that chance.

 

here is how my muffler works. i know this because we had to cut it to weld one of the plates which was off and making terrible rattling noise. i didnt expect to see something like this. can i gain some hp by puting a straight through muffler instead of this one?