01' Z28 A4, 93 octane, TSP lid, ported TB.

At high rpms the car is detonating. But it only does it when you stay in the higher rpms for a long time. From a dig it doesn't ping until it gets around 5000-6500 (once going like 65-70mph). I had a grantelli meter on it and it pinged. So I took it off and put the stock meter back on. It still does it. I'm thinking it's timing. Bought it used so don't know if the timing was advanced or not. The A/F is 13:1 all the way to redline. What the hell could it be?
Thanks. -Mark

EDIT: it pinged before I ported the TB.

 

What are you using to monitor AFR and also is there any knock retard? If the timing table was changed before you bought the car it could be running too much timing.

 

I don't have any monitoring device always on the car. I just dynoed it on a dyno jet and took the A/F reading from the tailpipe. How can I check if there is knock retard? Sorry still learning with these LS1's. Thanks. -Mark

 

you can only check for KR with a scan tool.