Is that only cause of the headers?

I've got AU type plugs in now and Pacemaker headers designed for E7's, I need to go back to EL2/ELGT headers now don't I?

Righto, im confused here.

Are your GT40 heads fitted to your engine in your car already? As in the car is/has been running with these heads?

And, no, the spark plugs have nothing to do with the headers.

Jeff,
After the recent top end rebuild, the pacemaker headers I put onto my E7's a couple of years ago were re-used, hence current trouble with clearance at no.4 & no.5 plugs & leads with the GT40 heads I now have.

These heads had the NGK recommended TR55IX iridium plugs for GT40P (1.4 gap) heads on there when I got the car back, not the NGK recommended BPR6EFIX-10 (1.1 gap) plugs for EB GT / ED SPRINT / EL GT

NGK recommended UR6IX iridium's were used on my E7's before.

I was told the heads are now GT40's, which have a recommended plug gap of 1.1 yet the plugs on there now are for GT40P's which have a recommended plug gap of 1.4.

I beleive my plugs are not the right kind for the heads I have?
Having GT40 heads, I'm basically running an EB GT / ED SPRINT / EL GT engine? as apposed to an AU I II III XR8 engine?

Car idle is a little too rough, tonight I found no.4 leads sitting on no.3 header and it's starting to melt it, so I'm going to buy another set of 9mm
Eagle leads to suit an ELXR8 before I change plugs?

it might help to look at the ignition system for each car.
If it was my car, i'd be matching the gap to the igntion system the rest of the plug to the heads, then play with heat range untill you get good burn on the plug.

^^^ Agreed. Use the correct plugs for the Dissy(E series) not coil pack( AU series). Gap them to suit the E series as well.
Brett