I use ARP. I know it's a premium, but I also know it is good stuff. $60 for some gorgeous stainless intake bolts that don't see much torque, but are right up front and visible- worth it in my opinion.
"The More You Know:"
As for hardware from the hardware store, be careful with certain coatings. Black oxide is the most common, and it is garbage since it is only a matter of time until they rust (further). Black Zinc is risky because cheaper BZ fasteners exhibit hydrogen embrittlement, and often cant reach torque yield values without shear fracturing. Reputable manufacturers use black zinc with no issues as the coating process is more controlled, so it is a safe fastener. Stainless looks nice, great corrosion resistance, but I won't use it in high torque or high strength areas (most SS hardware is similar to grade 5) but costs up to 4x more than low-carbon equivalents. Silver zinc is my favorite all-around, and honestly I don't know why it isn't as plagued by embrittlement issues as the black zinc (maybe because you don't see the ultra-cheap mfgs using silver zinc?).
When buying from a hardware store, like Midwest Fasteners and such, be careful about strength designations:
Grade 2: Low Strength
Grade 5: Medium Strength
Grade 8: High Strength
Class 4: Metric, similar to Grade 2
Class 8.8: Metric, similar to Grade 5
Class 10.9: Metric, similar to Grade 8
Class 12.9: Metric, exceeds Grade 8
Do not confuse 8.8 for Grade 8. Some places casually intermix the terms (such as "Grade 8.8"). For the vast majority of uses, it won't matter. Your intake wont care if you use Grade 5 or Grade 8. In my line of work, we've actually had to make our own fasteners out of Stressproof 1144 because 12.9 wasn't strong enough in certain applications.
