Help!

I make a batch of wine from Mosti Mondiale (www.mostimondiale.com).
It is 23 litres of frozen grape juice with yeast already added. To
make a long story short, those take 8 weeks to make. Mine is now 12
weeks old and still aging in the carboy. I've tested a sample
(couldn't resist) to find out that is not quite as bold as I would
like it to be. The wine is very good, better than wine from
concentrate kits like I used to do, but I want a very bold wine, the
kind that makes your jaw lock when you first taste it. Is there some
natural additives that can be added to make it bolder? Even if it
means leaving it in the carboy longer.

Any input appreciated,

Marc....