Hey guys. Car made 325 rwkw last tune and since then I have changed the standard cooler to a rapid v2 kit and 4" turbo side intake and walbro fuel pump. I have also put a new 35/40 on and done the coil packs and plugs. Had it all retuned today and couldnt make barely any more power. Tuner was shocked until he realized the exhaust was a 3" system. No cat just rear muffler. He then knew why it wasnt making power. I blame the previous owner for going 3" the banana lol. Where do I go from here and what power should I really be making? Is the 3.5 inch better flowing for big power or twin 2.5 inch. Other mods are 7psi actuator and 60lb injectors.Cheers

Seen plenty of 3" systems make more than 350rwkw but yet I had the same problem with my factory exhaust holding me back.

3.5 and twin 2.5 are pretty similar, just make sure you're upgrading the dump pipe as well

I was prettty shocked that it restricted that much. I was told that it's the usual case with the 3". Would the std dump pipe be holding me back that much aswell. My mate has twin 2.5 with stock dump and few other mods like external gate and is making 400rwkw through a 4 speed btr

Found a twin 2.5 and 4 inch dump for $500 second hand. Should do the trick. Also has quad tips

I was prettty shocked that it restricted that much. I was told that it's the usual case with the 3". Would the std dump pipe be holding me back that much aswell. My mate has twin 2.5 with stock dump and few other mods like external gate and is making 400rwkw through a 4 speed btr

External gate vented to atmo?

Standard gate on my car but mate I was referring to has external gate.

What model are we talking about here? Bxr6t? F series? I've heard the F6 setups rear of the cat actually don't flow too bad for 2.5 setups?

Ba f6 typhoon bud

My BF mk2 made around the 360rwkw with a hollow cat, changed to the xforce 4" dump with twin 2.5", still in the process of tuning but it lost a lot of torque down low, but breathes a lot better up top.. The force 'works' but If I were to do it again I'd look into the ces racing exhaust or herrods kit or something

Cheers. Useful info mate. Im aiming for around the same power level considering the mods I have. Will opt for basically the same setup you just mentioned in mild steel.