Should I mill my edelbrock performer rpm intake?

beanhead said

One more thing to consider is how the faces mate with the heads, angle-wise. AJ alluded to it earlier

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This was a problem for me after the first decking. One deck was high at the back. the other high at the front. And they were not at 90* to eachother. But I did not know this. So when I bolted on my cast-iron thermoquad intake, nothing "gave". But I didn't find that out until after the cam break-in, when it idled like crap.
After I figured it out, I bolted on an aluminum intake which twisted enough to do the job. The next winter, I yanked the engine and found me a different machine shop, who was able to straighten it out pretty close. And by this time I had me an AirGap! I was pumped.