I tested the following pipes my 2001 ec300. I did this on the same day, on the same trail back in '02...
fmf gnarley
messico
doma
motowest
The motowest focused more delivery in mid power and didn't deliver nearly as much, or as cleanly, as the messico or doma on top. Given this, my suggestion would be to switch pipes to either a messico or doma.
jeff