Turbo question

I have a piper turbo arrow with a TSIO-360-FB engine. It has the original
waste gate on the turbo, and an after market turbo plus intercooler.
I recently made a long trip, and got the plane up to 14000 for the first
time in a long time. I was having trouble keeping the exhaust temp down. I
had the mixture full rich, and the engine was only using 14 gph. It seemed I
could not get the mixture rich enough.

I don't remember this happening on any of my previous flights at high
altitude, but the previous flights were a while back. The plane behaves
perfectly normal at altitudes up to 10000 which is were most of my flying
is.

Does this imply something wrong with the fuel system or fuel pump or is this
normal behavior for these planes?