Loss some back pressure

[PacmanG8]

wsup guys

I had a question for some advice on what to do to get some back pressure back on my 08 G8. I just had flowmaster super 44s installed on my g8 and had the resonators removed to make a lil louder. right off the bat I noticed a loss in my lowend torgue and acceleration. i ask the shop i went to and they gave me a couple ways to fix it, first he said he could cutt off the pipe he put in place of the resonators and put two smaller size piping inside that pipe to try to pinch it to get some of the pressure back. also he said i could put a x pipe to help some my lil problem. Before i do anything though im gonna drive the for a few days to see if the computer will relearn the new exhaust and maybe that will help.

any advice

thanks guys

PACMANG8