Pinging/detonation question

[withamc]

Thanks 90LSC - I can hear some ticking while it's idling, but I can't seem to narrow it down to a particular point. I'm almost positive I've got some sort of exhaust leak, and it gets louder when it's under load. I'm going to clean everything up and put new gaskets on when I put the new H-pipe in, but in the meantime I'm trying to see if it's pinging as well.
When I first put the engine in, I kept the original 19 LB injectors with the SD set up, and I had to advance the timing to 16+ BTDC to get it to run decent. When I put the mass air in I changed to 24 LB injectors and I was able to pull the timing back to 14. That makes me wonder if I did some damage to the engine while I was runnig the 19 LB injectors.
Thanks for your help.

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86 GT, GT40P heads, Cobra cam, 1.7 RR's, Cobra intake, 65mm TB, 73mm Vortech, 24# injectors, 2-1/2" BBK H-pipe (w/cats), Flowmasters, 3.55s.