I was reading up on the turbomustang forums about blowthru setups and they said not to use any holley pumps. Is that just a preference or is there something else that may go wrong?

http://www.turbomustangs.com/smf/index.php?topic=23311.0

all your answers are in there

JUNK....would you even use one N/A?

Holley pumps don't do enough pressure. Your pump needs to put out pressure for the carb + plus as much pressure as you plan to boost to keep up with your 1:1 rising rate fuel pressure regulator. So if your carb needs 6psi to run n/a and you plan on running 10psi of boost, your fuel pump needs to do 16psi and flow enough GPH of fuel at that pressure to supply what you need for your hp level.

DT... lots of guys use mechanical pumps on blow through engines. Put boost pressure into the atmospheric port and it works just like your fuel pressure regulator. When boost goes up, fuel pressure goes up.

The Carter pumps seem to get the nod over the Holleys.

Yeah I was thinking electric. OP didn't say either way.