1) Whats the level and blend knob setting?
The above 2 will affect the dry and wet signal ratio. Need to balance it out
and no, true bypass is not to sort out volume issue when pedal is activated! Duh..
True bypass mod is a mod that take effect when your pedal is not engaged(totally opposite of what threadstarter wanted, when wanna activate the effect), so that your guitar signal will go from input jack to the output jack directly, without going thru active circuitry.
Imho, dont waste money and blindly look for the true bypass mod, without understanding what it does. how it affect signal chain etc
do a comparison with another dmm at similar setting. If theres still a volume drop, there cud some other issues.
Look for goosonique or randolf in the forum here(search for their name), They shud be able to help.