[stuartbrown.e90]

So this may be a stupid idea, but I’ve been thinking about using the MHD 2step/launch control to blow out my cats. I purchased the VRSF catless downpipes a few months ago, but when I went in to install them I found that the car was so rusty and corroded that I would have to saw through the downpipe to catback section, replacing the whole exhaust, and essentially have to pull the motor to separate the turbo/downpipe connection. Since I don’t have a shop myself I would’ve had to pay to have it done which would be wildly expensive.
That brings us to my idea, I have seen multiple videos online of people using the 2 step on n54s to simply blow the cats out the back of the car. I was wondering if anyone had ever tried this or had some input on it before I try… I am currently running around 18psi on the stock turbos and have a big intercooler as my mods. Would love to have the cats gone for max power gains and sound but I just don’t want to spend the couple thousand dollars to pull the motor and buy a whole new turbo back system.
Thoughts?

[dmckmc]

have not heard of this before. i'd be concerned about simply clogging/blocking everything if the substrate breaks loose. wouldn't it all be caught by the secondary cat? the risk/reward would not be there for me.

[stuartbrown.e90]

So I’ve already done a muffler delete and am thinking about doing a secondary cat delete as well. Could risk getting clogged but would the 2 step not blow out the secondary cats as well?

[lookalikehuuh]

Have you also seen the videos with the engines blowing up due to 2 steps because that is much more likely IMHO.

[kevlarblue]

There's gotta be a way to free up those bolts so you can install the down pipes. Have you tried PB Blaster or rusteez? Drilling the bolts out? A sawzall to cut through the bolts inside the flange?

You can get the turbos off the motor without pulling it out and the down pipes are attached to them. So if you get the exhaust separated you could just cut through the v-band clamps to get the down pipes off the turbos.

I would be trying a lot of these things before blowing the cats out of the exhaust. I don't think that's going to end well.

[stuartbrown.e90]

We’ve tried just about everything to get the downpipes out. The downpipe to catback connection is basically fused together from the rust. It’s so bad that the bolts are nothing more than little rusty bumps. The only way I would be able to get it off would be to saw through it in which case I would have to buy a new catback system. And even if I got that one off the turbo connection is just as bad. I tried for about two days to get it off myself before taking it to a well respected shop that exclusively does bmw/audi performance and they couldn’t get it off either without sawing through it and pulling the motor, and I wasn’t willing to spend that kind of money just for downpipes.
The cars first owner lived in boston for the first 14 years of its life so the rust/corrosion all around and underneath is pretty gnarly. I’ve decided that I’m just going to wait and when the turbos eventually go out, I’m just gonna replace everything at once with the downpipes and a whole turbo back exhaust. The car has around 110k miles on it and the the is already smoke a little bit running at 17-18psi.