bfly

I spent my Saturday removing my down pipes, piggifying and reinstalling them. Piggy Pipes (cheap Chinese knock-offs) are the best bang for the buck you can do to a S4. I have the cost of O2 sensor bungs($5) and a Saturday worth of time invested in them.

There are few HP gains that can be had for such a small price. The aggravation of removing the top DP bolt on the driver side DP is another story. I was worried about piggifying the DPs not removing them, what a PITA. My hat's off to those of you who have done the job on the ground. I wouldn't even attempt it without a lift.

I really don't know what the HP difference is, but what I can say for sure is it helped the turbos spool up quicker. The power comes on about 500rpms lower than before the piggies. It is a great mod if you have the tools and lift at your disposal.

Angular

What technique did you use to remove the pre-cat core? Major PITA!

Funkweasel

center of the cat. Then punch it out in three sections with a large screw driver. You can leverage and tear most of it out that way pretty quickly. Then just use a flapper or wire wheel on an extension to clean up the bits and pieces left on the walls.

ymmv.

Angular

Hmmm... I may have to try that on the next one.

bfly

I drilled multiple smaller holes and then drift and air chisel.

reefer_bob

Air hammer sounds viable... but I don't think any of my bits are long enough...

PT S4 BC

What size bit is required for the O2 sensor bung ?Do I need a gasket at the turbo?

bfly

I used a step drill bit (unibit) and reused the turbo gaskets.

reefer_bob

Do you have a welder too? I can't weld.

bfly

I did all the work at a friend's 4x4 shop. So yes, I had a very nice mig at my disposal.