I thought you lose quite a bit of low end using a 4-1 header...even though you gain on the top end of the power range...4-2-1 should give an even, smooth boost throughout the RPM band.
You should splice it inline with the existing wiring...so I would go with number 1.
I used a 1.2K resistor spliced inline ($1.00) to fool my ECU that my shop installed when i eliminated my factory cat with a HS header.Hope that CELE was cheap,I have seen some run up to 80 bucks.I still had to...