What gap and boost are you using ?You may want to close the gap slightly.
I had the same problem with a new set of Champion Gold plugs ages ago when road tuning the TC on app 8psi + boost .(Was fine on normal everyday driving) and closed the gap to 0.8mm =end of problem :)
FWIW I now use NGK Iridium or NGK V groove plugs.
I've had mine since 03 07 92
85 JB 2323cc DOHC 4G63
THE OLDER I GET THE FASTER I WAS
GROWING OLD IS MANDATORY GROWING UP IS OPTIONAL
Problem solved. It was the vacuum line that runs from the inlet manifold to the box on the firewall near the master cylinder. The hose was rubbing on the heatshield and it wore hole right through it. Was missing like a bugger. 2 second fix and went for an awesome drive in it today. Couldnt believe how great it was to drive it out on the backroads of kurrajong where I live. I am very fortunate to have clear country roads around me anytime I want to go for a drive.
