I just finished installing a 3.4L whipple on my 03 Cobra. Along with the whipple I also upgraded to Ford GT Fuel Pumps, Dual fuel pump driver module kit, 60lb injectors, cpr fuel rails, metco underdrive crank pulley kit (this was installed to bring my boost down. I was putting out 25 lbs of boost at 4500 rpms and my mechanic thought that was too dangerous), SCT Big Air 2600, and Fore Billet Fuel Cat. I also previously installed long tube headers, xpipe, catback exhaust, CAI, accufab throttle body. It is tuned to run rich to be on the safe side. I am putting down 618 rwhp, 580 ftlb, and 19 psi. What problems can I expect? My mechanic told me that I could break my axle. I do not plan on running it on the track anytime soon without beefing up my rear end. Also when I am running through the gears going form 2nd to 3rd to 4th I feel like it is puttering a little but not too much. It just doesn't feel solid. It feels like the car cant handle the power. Why is that?