Turbocharged Manifold Pressure

[mshac]

My rear engine manifold pressure has been a little flaky lately. The gauge will fluctuate between say 29 and 31 inches in high-altitude cruise. I thought it was a sticky indicator gauge. It wouldn't do it all the time, but I did notice it.

The second to last flight, the rear engine would never make the same MP as the front at the same settings. It was about 2" lower. Again, I chalked it up to the gauge.

The last flight, once I got to cruise altitude of about 16K, I noticed the rear MP was at about 25" when the front was at 30". Again, it would fluctuate between about 23"-25".

My normal cruise speed was knocked down by about 15 knots, and the rear engine ran much cooler than the front at the same fuel flow settings.

The rear engine makes normal MP at lower altitudes.

So my question is this: Where do we begin troubleshooting?

The problem could be, IMHO, one of the following. Feel free to add to the list or expand on the correct testing procedures:

1. Cylinder(s) with low compression ( I'll do a leak-down test this week)
2. Intake manifold leak
3. Bad controller
4. Exhaust leak (prior to the turbo)
5. Bad turbo

Anyone with any experience chasing down this type of an issue, please chime in!!!