Hey guys I have a 2001 9-3 with a tuned B204.5R. I pulled the spark plugs and noticed the gaping was less than stock on all of them. Is this a sign that I melted them? should I be checking the pistons now?
How tuned? HP? Like Josh said, .9mm is the usual preferred gap for most of us. Stock is 1.0 or 1.1.
I'd guess your pistons are fine, but run a compression test with a hot engine if you have concerns. Wet/dry. FWIW - unless you're running very high HP, the pistons are usually fine. A bad MAF can burn them or the valve though... so it might be worth replacing it if you never have - especially with a tune.
Always compression test and smoke test first . If compression is not good and equal across the cylinders then do a leak down to establish where the issue is , valves or pistons. . Smoke test for leaks. If good on all fronts diagnose further. The spark plugs center porcelain will show silver specs under a magnifying glass and / or the ground electrode will be closed up or gone missing. Hope for the best