If you don't have access to a wideband (either dyno or mobile), you can get an idea
by looking @ your plugs.
Black - rich
Brown - good
White - lean
Of course this isn't going to tell you that you are lean @ transition when your boost spikes to 14psi right before your motor pops...
My suggestion, spend $1000, get a PFC. It's cheaper than a new motor and will gain you some additional (safe) hp!