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[doolie72]

So car has been running fine for a few hundred miles since replacement of plugs/leads/dizzy cap/lambda sensor/fuel filter It’s now developed a slight hesitation around 2000rpm on full throttle. Eventually the boost comes in after a couple of seconds but it seems a little down on power.
After some forum searching I carried out the following checks:

Plugs ok (Regular colour)
Vacuum leak test ok (using the starter fluid method)
Ignition Timing ok
WOT switch ok

Any other culprits I should look for? Could it be sticky wastegate or a clogged lambda sensor?

[bureau13]

Do you have a boost gauge? I find it almost impossible to diagnose turbo issues without one. Even if it's a temporary install where you route the vacuum in via an open window or something, you can learn a lot about what is going on with the turbo/wastegate that way.

I had some weird behavior that I thought might be the lamda sensor. It wasn't the same as this but you can unplug the lambda and run it and see if the problem goes away or changes. I ended up installing a wideband and not bothering with the emulated narrowband signal at all, so as far as my car is concerned there's no longer an O2 sensor at all.

[doolie72]

Problem solved! Looks like I may have filled the tank with low octane fuel. A can of octane boost did the trick.

[Mike9311]