Hello,

Installed opti, plugs, wires, coil and module last August on a 99k mile LT1. I used Autolite XP106 plugs gapped at 050.

Ive put maybe 1k miles on the car since and its starting to miss. If it is lugged down (like 2k rpm) and i increase throttle, around 1/2 to 3/4, it pings and misfires. 

It feels like i have a bad plug or plugs. 

Also, i forget, but I think i used 87 octane. 

My plan is to finish this tank and put some 92 or 93 in to see how it feels. 

But, im now curious, anyone have any experience with the XP106s? Ill follow up with higher octane fuel results. 

Does the 92 vette have a more aggressive timing/fuel curve than 93? It feels faster than my 93s and gets consistantly lower MPG, but should be same. 

Thanks,

Chris

Sounds more like a bad fuel issue, considering it's not been driven much since the work was done. I would first drive(or siphon) out the fuel that's in it, and fill with fresh fuel, and see how that works after putting a few miles on it. Another problem could be water in the fuel from sitting. Start with fresh fuel....

Joel Adams  
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Hello, funny you mentioned water in the fuel. I washed it the other day and found water pooled up in fuel filler area. 

Same thought crossed my mind.

Ill let yous know results. 

Check your owners manual for fuel requirements.  I would never put regular gas in your car.

Well,i feel a little slow. Fuel was my problem.  I put 9 gallons of 93 octane in and it runs great now! 

Woops, lesson learned, LT1s need the expensive fuel! 

Thanks!

Chris