I dont' see why putting an intake in makes your car leaner. The ECU will sense more air coming through the MAF so it will bump up the fuel it throws in. Thats how mine is..it actually ran richer. Maybe if it annoys you, take a trip down to ecu reset and see if it keeps backfiring for the week or two while it relearns everything.

 

the reason why you have afterfire is simple. forced induction cars run rich from the factory to begin with in order to keep cylinder temperatures down and cool the piston, as the reason is with GDI technology in some cars. all cars have afterfire due to much of the fuel being dumped out the exhaust, the only reason why you can't hear it is because the catalytic converters absorb much of the noise and fuel being let out the exhaust. now, a blow off valve will cause you to run a bit more rich on fuel only between shifts, which is a split second or two, so this isn't detrimental to the engine or anything, however, due to this richening, much of it is dumped into the exhaust as explained and when it comes into contact with a hot spot on the exhaust, kaboom, afterfire.

in terms of the lean effect with intakes is due to the fact that the MAF sensor sends air flow signals to the ECU to determine proper fuel delivery. now, if more air gets past the MAF, the ECU doesn't detect this and computes only the air that was registered, therefore more air and less fuel equals leaner conditions. this can be mainly due to the fact that the stock intake has a smaller diameter than most aftermarket intakes, therefore, it's safer to use the stock intake, which many have said and is proven to be good for at least 350hp or so. why fix something that isn't broken? that's just a theory

 

This is correct. One of Vishnu's prototype stage III cars makes well over 300 wheel hp on pump gas with the stock intake. It's not a barrier to the power the average modder is looking to make. Your fuel rails and intercooler will fall short before the intake does.