Having searched around a ton, and read a bunch of reports, I keep seeing mixed messages about SM needles. Did a clean and refresh on my SU's this weekend, and installed the SM needles that came with the z therapy kit.

Nice improvement. Above 3k, she wakes up a bit more, and pulls harder. Fuel mileage is up as well.

But I keep reading that they are all kinds of bad in the long run. Trying to find any other needle is seemingly very hard to do now.

Anyone care so shed some serious light on this? Why would they include it if its capable of more harm than good?

I dont really see why they would be bad on the long run. I have SM's as well. It richens up the mixture in higher rpms and gives a bigger kick than the oem needles. In my case, my fuel mileage has gone a little poorer even we tuned my carbs with colortune. I guess that is the only bad thing i can found.