Chris, I've used TCP in my LNC2 for about 10 + years. No known down-side
other than the cost of the stuff, which isn't all that much when considering
the benefits.

I started using it in my Lancair after having problems with severe lead
fouling in my small Lycoming. In one instance, which convinced me to give
TCP a try) I had a glob of lead completely short out a lower plug. The glob
of lead looked like it had been melted into the electrodes with a welding
torch. After I started using TCP I have had no further lead fouling problems
in over 7 - 800 hours. As I understand it, TCP interacts with the combustion
process to turn the lead (in our so called "low lead" fuel) into a soft
compound that is readily scavenged during the exhaust event.

For some reason, this engine (an O-235-L2C) seems to have a real problem
with lead fouling, even when using plugs (Champion REM37BY) that were
supposed to have been specifically designed (or so I'm told) to help with
the problem. Though I don't have direct evidence since I haven't had my
engine apart, it's likely that TCP will also keep the hard lead deposits
from building up on the exhaust valves - which an old A&P friend once told
me can initiate pre-ignition under some conditions.

Incidentally, many years ago I often flew a Piper Tomahawk (which uses
basically the same engine as mine) and the FBO owner insisted that TCP was
added whenever it was fueled.

Whether yours' or any other engine needs the additive, I have no idea.
However if you're noticing enough lead fouling in your plugs to cause
problems, IMO, adding TCP will help.

Hope this helps.

Dan Schaefer