Do after market spark plugs actually increase horsepower, has any one switched theirs and is there a difference ?
If so witch ones are the best, thanx.

aftermarket spark plugs are gay,they dont work and they make your engine run hot.for the best performance put in the recommended replacement plug ngk.have 2,000 miles on my 03 impreza,went from crap champions to the ngk replacement,huge difference in idle and hp

I agree w/ 03impreza2.5rs. Plats are for people that don't want to change their plugs often. Copper conducts better but you should change them more often.

I just use NGK Copper and change them every spring. More often than needed but for ~1.50 usd each it's not that costly.

thanxs for the props peaty

NGK copper plugs work great for me. Not sure if I got a hp increase but I have peace of mind. I got the plugs that are 1 range colder than stock so as to keep engine gas temps down.

I'm going to make this swap. Excellent.

What's the designation on these plugs?

Thanks in advance.

--BA

http://www.scoobymods.com/forums/showthread.php?s=&threadid=166

Great info. Thanks!

--BA