Running Sluggish

[kevin65124]

Hi,
Well recently my 68 has been running a little sluggish in the mornings or sometimes if I havnt driven it all day. It will somtimes backfire through the exhaust. I took it in to get the brakes checked and get a tune up. I was getting the tune up cause I thought that was the problem, well it didnt need a tune up. I was wondering since my exhaust just exits through Hedmen headers and then 2 1/4" pipe then flowmaster 40 series that exit right past the cab. Could the reason the engine is running sluggish be that I am not getting enough back preassure?? Should I run a full lengh exhaust system? Cuase I really need to get the thing running better.