With just over 4,000 miles on the long tubed headers on my '99 C5 made by TPIS,
I found all airtubes that are welded into header tubes have cracked and sucking air.
This requires both headers to be yanked and re-welded. That's about 8 hours labor in total plus the welding costs and the hassle of finding someone that does this type of welding.

This is not what you expect for a high priced
part, esp when that vendor spouts quality.