I had a very similar problem and it turned out to be a clogged cat.

DannoXYZ -

Thanks for the rundown. Have purchased a 4x4 junction box cover - nice trick. I was always visualizing a thicker plate with the pipe behind removed, but you've solved that by sandwiching.

Will thereafter take a look at the downpipe / cat. I had the turbo off 2 years ago, annoyed that I didn't look down the downpipe.

Will have to figure out where the downpipe separates from the cat

My car was maxing out at 5psi....found it to be clogged cat. I actually put a piece of steel across the WG's piston to stop it from opening period, still did not fix the boost. When I finally took the cat off it was almost totally blocked. This was a piece that came out of the cat.
Sox
http://forums.pelicanparts.com/uploa...1418276858.jpg

That was the answer! Took the cat and downpipe off, car acceleration and boost were all there. And it was loud! Prior to that, I had blocked the wastegate off with a flange, did not make a difference. Man, was it exciting to drive the car with full boost - I wanted to stay out longer, but it was going to break some windows if I did. I've been looking for this issue for at least a year - Danno, looks like I owe you a beer if you find yourself in Boston!

At this stage, unclear to me if its the downpipe, the cat, or both. Here's the evidence:

1. Can't roll a golf ball through the downpipe (diameter 1.68 in, but I could put a flashlight through (diameter 1.25in). External diameter of pipe is 2.12 in, so seems likely it collapsed at the corner, where it goes from vertical to horizontal under the car towards the cat.

2. I was able to see light through the cat - like 16 pixelated cells out of 10,000 - see picture below. Surface didn't "look" clogged. First picture in cat is with flashlight on engine end, no light used on rear end. Second picture includes light from rear as well, to show relative size of 'light hole' coming through the cat.

So my hypothesis is just downpipe, which means I need to find a muffler shop to cut it off and weld in a new section? Or better to but a new downpipe?

http://forums.pelicanparts.com/uploa...1418508354.jpg
http://forums.pelicanparts.com/uploa...1418508376.jpg
http://forums.pelicanparts.com/uploa...1418508397.jpg

Reading RL, technically I should be calling this the 'cat-pipe'. The turbo outlet pipe is still on the car, and was not collapsed.

I have the pipe you need that was removed at 70k. The cat was replaced 1k miles before I removed it so it is almost new.

PM me if interested.

Glad you found it!

Also thanks for sharing your efforts.... Helps us all build the community.

Mike

Glad you found the problem! That section between the downpipe and cat is problematic. It gets crushed easily and can collapse internally.

We used to live in Boston! Cambridge actually back in the '70s when my dad was at university. Looking forward to visiting some time; I miss the snow! And I skating on the Charles!

Uh-oh! Found out tonight that I also needed the cat-back exhaust. I put the new test pipe on, with no change. Took off the muffler, full power. Annoyingly, the top section of the exhaust muffler pipe was collapsed, from below it was still round and intact.

Will now be looking for mufflers!

That sounds like your catalytic converter honeycombs have fallen apart and blocked your exhaust.

I have never heard of a cat-back collapsing due to heat, only the catalytic converter pipe, and only in high HP situations.

I was surprised as well. However, it is not the cat, because I did the test last night with the cat-pipe installed, only the muffler removed.

If I get a chance, I'll post a picture of the the collapsed muffler pipe tonight. Was not a stock muffler, was an ANSA.

New muffler is on, all other pipes the same, and car is working great ! So it was definitely the muffler. Going to have some fun cutting it apart tomorrow to figure out.

For interest, here is the muffler that was blocked. Chock full of knotty fibre.http://forums.pelicanparts.com/uploa...1421201933.jpg

What is that? Did the muffler come apart internally?

Could be a fibreglass-packed muffler. Could've gotten blown around over time and clogged one end.