Okay i have a 2000 Focus SE and i just put a Flowmaster catback exhaust on the other day. At first it was kinda quiet but then i let the gas run out and put 93 grade gasoline in. It sounds a whole lot better but the downside is when i rev; the RPM's drop down and theres low popping or grumbling sound like a Honda with a 3.5 inch exhaust smh. My friend told me that i may be running rich; because i do have a huge problem with gas and i need to replace my plugs because the maintenance of this car wasn't done entirely before i bought it earlier this year. What by this what do you think my prob is?
what else could i do to boost performance after this. I also installed a Steeda CAI.
im trying to get to at least 250hp by this upcoming summer.