Okay so im ordering headman headers soon. i opened up my truck by puttin 40 series mufflers on and its running alot better right now im waiting for the headers to come so i can get rid of my cat. cause i do believe its clogged up also about 2 weeks ago my truck started to backfire while im driving, is that because of the cat. because this started before i put the flowmasters on. Also what would cause it to do this.

I'm still in highschool 12 grade and so i dont make that much cash i just quit my job for doing drywall and now i do deliveries for a pizza shop i make alot more now and its a steady flow of cash I make about 300 a weak without tips so if you guys know and cheap mods to make me run better let me know thanks

just so you know here is what i have so far on my truck.
K&N
Accel u-grove plugs, wires, and cap
flowmaster dual 3" 40 series
3" sunpro tac
each fill up i put in either STP octane bost or EFI Cleaner


Soon to get are Headman Headers and 3" cowhood also if anyone knows where i could get a Ford Lightning '92 for cheap thanks