I was going to put them on myself and noticed that there is a sensor on the stock header like 8 inches from where the header meets the block. So....does a hole need to be drilled and threaded into my new 4-1 header???

 

Also....what are the pros and cons of a copper gasket?? And what about the different diameters??
Thanks

 

You need to extend those sensors.

Don't bother buying new gasket. Currrent one is more than enough to meet all your need.

 

That 'sensor' is one of your two o2 sensors.

You have to relocate both o2 sensors, and at least ONE if not BOTH of the cats.

The the 1st o2 sensor should be in front of the first cat, and the second o2 sensor should be after the first cat (or inbetween cat's 1 and 2 if you use both).

 

Allright, I measured my piping on the header also and its 2.25 and not 2.5, i thought it was supposed to be 2.5?? I have a 2.5 cat coming and now everything is going to be different sizes!!!

 

relax. Your exhaust shop can make it work.