Well, she didn't like that last spray!
Knocking in the engine right after the 3-4 second nitrous pull out of many done in the past, so that was odd.
Turns out it was a colapsed valve lifter. Replaced it and boy, was that FUN...
Taking off the valve cover, all wires, and engine harness, getting the lifter and rocker out WITH the engine in, the cam and everything still in was a very hard and tidious process.
Took a while, but eventually got the new lifter back in! After countless tries without a valve spring compressor we made a custom tool to push the spring down enough to get the rocker arm back on. Never thought it would be so hard to get to it. 
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Nitrous vs. Valve Lifter...
