TimmydRX8

Hey I have had my 04 Rx8 GT 6spd for about 4 months now, and it was driving fine for the 1st 3 months but lately it's been feeling as i accelerate that the engine is struggling, a feeling like it is bogged down. Also i've noticed tht it is cranking a bit long and the crank sound is different from how it used to. The other day i rev'd it up to redline while sitting idle in a parking lot and on its downward descend from the rev the car had backfired, i did it a couple of times nad it kept back firing. To add to these other problems, i'm having rough idles not only at stop lights but at time when i'm not getting on it. Anyone have any ideas to what could be wrong? Thanks!