honestly man, coming from someone who loves his legacy, you bought the wrong car! our car is a huge boat and short of engine swapping or fully building the engine/tranny, youre not going to get a lot of power out of it
just buy a replacement flasher relay that goes under the dash thats made for LEDs...that way you can replace any and all bulbs in your car w led without any issue. Also Lasfit makes high quality leds that are internally regulated so no resistor required. I have every bulb on my legacy inside and out replaced w leds for well over 4 years with no issues
not HPS but I have the injen intake and have had it on the car for 7+ years. You wont have an issue, you wont have any power gains, you do not need a tune for an intake
no theyre the same...our DRL/high beam are 9005 and thats whats in the OP's link as well
our low beams are a diff bulb type if thats what you mean. I also run vleds in my DRL like corey