I took the 951 out for some driving today. It sat for around 6 months. I have to replace a gasket (o-ring) on top of the turbocharger (oil supply line) as it leaks and coats the turbo with oil. Had a bad smell and some smoke coming off the turbo initially that slowly went away the more I drove it. That should stop all together when I replace that o-ring. I put fresh oil in before storing the car, and it is still topped off.
I'm going to take it to work tomorrow morning as everything feels solid. When I get back tomorrow afternoon, I will remove the throttle body and replace that o-ring. Hopefully I will be able to reach it with the throttle body off.
I have an Autothority maf/intake that has the car putting out 252rwhp. Also a Lindsey Boost enhancer that is not increasing the boost.

Issue 1 - Occasional rough idle mostly at startup (up to 30 seconds+??? sometimes - I never timed it)

Occasionally, the idle is rough when I first start the car. I have tried adjusting the autothority potentiometer rich-lean and it doesn't seem to help the idle. I don't see any cracks in the vacuum lines. Sometimes it is rough during hot start up.

Issue 2 - sometimes boost isn't smooth, or fades away

This doesn't happen consistently so it is difficult to diagnose. I can hit full boost nice and hard up to near redline, switch gears and hit boost while it is pulling hard and then suddenly it feels flat so I'll ease off for fear of damaging something. Or I may have the car in 3-4k rpm where it is suppose to hit boost hard and it may take a second or two longer than normal to reach full boost compared to the usual instant boost. I'm not sure what is causing this but perhaps it is related to the occasional rough idle at start up. I'm feeling it may be a vacuum leak. The turbocharger has no shaft play and the intercooler pipes just have a light coating of oil, nothing extreme. For the most part it boosts smooth, and hard. These are just occasional incidents.

History:

I have owned the car for 4 years and 30,000 miles and the previous owner has owned it for 4 years and 30,000 miles. The previous owner never heard of the venturi delete so I believe it never had that update. Would that cause this problem? I also have a throttle body reseal kit I plan to install after I remove the throttle body tomorrow afternoon. Maybe I will hold off replacing the o-ring and throttle body seals to order a venturi delete kit if you think it maybe that.

Thanks

 

It could be the ISV, or a vaccum leak your not noticing.