I have the somewhat underpowered 4.6L and want to either maintain current stock low end torque or improve it. I have decided to go with magnaflow because of their dyno results. My question is: which will produce the better results SI/DO or SI/SO. Again I do not want to sacrifice any low end torque. Also I have the Air Force One Intake and the Superchips Tuner from Troyer Performance(wasn't sure if that made a difference). Thanks for any help.

 

i believe the 3" SI/SO is the way to go. i would call Mike at Troy and ask him if your not sure. he's the man in the know, especially since you have his chip. you'll have to reprogram your tuner after to get full benefit of the new exhaust but i'm sure you already knew that. the tuner from Troy is my next step as soon as i can afford it.

 

Well called MagnaFlow directly and spoke to their technician. He stated that with duals it creates a more flow throughout the exhaust. He said this creates a loss of backpressure and therefore a decrease in low end torque. He recomended the SI/SO system to maintain my low end torque. Also stated that duals a 5.4 does not create a huge defecit in low end torque like duals on a 4.6 do.


Do you think I will have to have Mike retune my programmer?

 

I am going with a Magnaflow SI/DO #12158 mostly because of the duals look. If I get a decrease in low end I will try to get it back by other means. Choose 4" SS slash cut tips.

 

You got the 5.4L, so it won't be that big of a lost. My dad has glasspacks on his 5.4L and I could not tell the diifernece in torque. The 4.6L I have is another story.

 

i would think if you want the full benefit of the exhaust and the tuner i would have it reprogrammed. if it was me i sure would. you might want to post this question on the chip forum. there's a pile of guys there that are a lot more knowledgable then i am on this subject. Mike might even reply back to your question himself with his recommendation. good luck.