<951>

I have an 89 951 with a full 3" exhaust and downpipe without the cat and chipped to 15psi. When i first installed the k27/6 and exhaust it spooled up very quickly. After a while it seemed to get more laggy. Now it barely reaches 15psi at 5,000 rpm and sometimes it will only get to 12 or 13 psi.

When I installed everything I replaced all of the exhaust gaskets and I have checked my vacuum lines countless times.
Could these be the symptoms of a collapsed crossover pipe?

shortyboy

How long ago was the install? Was it a new or used turbo? Usually causes for a large turbo could mean exhaust leaks, check that first. Then vacuum leaks. That could also lead to lag. Worse case you need to rebuild your turbo.

Auto_Werks 3.6

Check wastegate function as well.

refresh951

Pressure test the intake track also as shown here to check for leaks:

<951>

The turbo was freshly rebuilt and balanced. Thanks for the suggestions I'll check those things when I get the chance

Humboldtgrin

+1 wastegate

mr965

check the hose on top of the diverter valve (BOV) and the hose.

Paulyy

wastegate. I had mine slowly come undone and lag got worse.

raleighBahn

Wastegate easy to check - see Clarks Garage for low boost / checking wastegate write up.

Humboldtgrin

You can also take off the wastegate realy easy and make sure your valve isn't burnt or valve seat cracked. Also the BOV is a good check as mentioned before. Low fuel pressure maybe? Clogged fuel filter? Calapsted pipe maybe. Start with the BOV then wastegate then fuel filter then exhaust pipe inspection. Take off the intake to the turbo and check the turbo shaft for play just in case. After that I'm at a loss without the car in front of me.

<951>

I removed the wastegate and saw 4 small cracks in the valve seat, everything else appeared to be fine