I have the same set up on my mustang and it was doing the same thing as your car is doing and told my buddys dad work at ross labs and we was talking about it so he did a chemical formula equation balance test and found if u add E85 with 87 octane it will even out the nitroglycerin fuel systems upgrade and make it run good. I found the kit was good for tons of torque and ok HP . Also look into running some cold spark plugs.