To the OP: Congrats on your new ride. You won't regret having a turbo.
Book speeds are, in my experience with an M20K and now an M20TN, optimistic. Both my planes had/have TKS, the book speeds in the TN are calculated with the step removed, etc, etc. I flight plan 5% under book speed and slightly less fuel flow.
Some things to consider:
I'll second the recommendation to get a modern engine monitor - and especially one that logs data.
Check all your gauges: Is the fuel flow reading correctly? Mine on the G1000 wasn't (dirty connection read a few GPH low). The TIT sounds low.
While there are no live APS classes now, perhaps the online course is still offered. It is very worthwhile in understanding what's happening within your six co-joined power plants.
I don't know if the TSIO520 in the Rocket will run LOP. If it will, that is a great SOP. You can much more easily diagnose ignition and fuel distribution issues LOP, the engine will run cooler, life will be better.
LOP, you set power by fuel flow, not by MP/RPM/Fuel flow. The charts that come with the Acclaim are silly in this respect. Get your engine operation manual from TCM (I have a soft copy I can share), and fly fuel flow.
Ignition issues:
15,000 is pretty low to see arcing/crossfire in the mags
+1 on the fine-wire plugs. They are standard in TSIO550 Platinum engines now
LOP mag check will tell you very quickly if you've got a harness problem, bad plug, etc.
I would defer spending a lot of time diagnosing this stuff (except maybe checking fuel totalizer K-factor and TIT reading) until you have a good monitor and logged data.
Enjoy your new plane!
-dan