Power Loss After Installing Aftermarket Exhaust

[i've seen the light]

hello.

i have an 06 f250 CC 4x4 which was all stock except for cat delete, airaid air filter, and sct programmer with idt xtreme race tune. it had plenty of power. would beat any dodge you bring. i decided to install an aftermarket turbo back exhaust with 3.5" downpipe and 4" back. the truck is much slower now but i got about 1 more mpg. im not crazy about the mpg. i just want the power back.

this might be a dumb questions but do i need a new tune to fix this problem?

[Turbolag87]

Im beginning ot hear this very often lately, bigger exhaust means Slower truck specially on the lower end.