420A 420a turbo custom exhaust

[SilentSilver]

Hey everyone after driving my now turbo 420a with just a downpipe its obnoxious having it dump up front so I'm going to be welding a custom exhaust. With that being said I'm going to put the upstream O2 back in so I'll be welding a m18 x1.5 bung on. Is this the correct size for the stock O2's?

For my exhaust I'm going to put a test pipe in to not foul the cat with fuel but don't want the ECU to see its running that rich and try to pull fuel, is there a simple way to bypass both the upstream and downstream O2 while still shutting off the CEL and allowing the car to run more than just a fail safe map?

Any input on this is appreciated I'm no tuner and only know the very rough basics

 

[BLACK'98DSM]

Wait, you're not running an upstream O2 right now? That's not good, you need that.

The downstream O2 can stay out though. It's not necessary.

The best way to get rid of the CEL is to remove the bulb from the gauge cluster.

 

[SilentSilver]

Yes not running the top O2 isn't good. That's another reason I'm building this exhaust, plus I have to pass a emissions test next year so the cat needs to be able to be pulled in and out relatively easy. Plus need the bulb in there for a bulb check. So I need a way around the downstream seeing no cat and don't want the upstream to try and pull fuel and lean it out since its running so rich off the FMU since I'm tied into the stock FPR

 

[SilentSilver]

Got it done, tight fit but working very well

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[BLACK'98DSM]

Looks like it hangs pretty low, just be careful not to bottom out.

I think I still see an EGR tube, I definitely still see the solenoid. You could get rid of that stuff easily and block off plates are cheap. At this point it's just an extra spot for boost leaks to occur.

 

[SilentSilver]

The exhaust hangs above or at the same height if the crossmember the intercooler pipe from the turbo is a bit lower but so far no issues bottoming out. I could block off the egr but it's disabled now and I don't see a need to block it plus one less emissions component to put back on if I have to get it tested at a facility