Weber carb underfueling nightmares

Right then… In dire need of assistance with some carb issues.

My mk1 is a 1.6 8v on twin weber 34 ict carbs, when we bought the car it barely idled and was really hesitant under acceleration.

Took the carbs off, re-jetted them using info on jetting for a 1.6 air cooled engine, fitted new gaskets and air filters and cleaned them up.

She now idles a lot better, quick poke of throttle to start and she idles at around 1000rpm, however when you accelerate past 3k the left carb as you look at them throws out a massive pop.
She ran fine for a few miles before the alternator died, so it's got a new alternator and I've replaced the vacuum hose between the brake servo and inlet manifold, since then this misfire has appeared, she's also got new leads and plugs.

Anyone care to share their opinion? I'm assuming the pop is down to under fueling, so there's too much air getting in somewhere yea? I've wound the mixture screws out as far as they will go and it still does it, I've re-tightened all the bolts and checked for leaks around the base of the carbs and still no luck, Could I of fitted the non return valve on the servo vacuum hose the wrong way round therefore letting air in? Does anyone actually know the right jet sizes for ict's on a 1.6?

Help!

have you had the timing checked?
also do you own a beetle with an 8v engine as mk 1 golfs are water cooled not air cooled.

have you had the timing checked?
also do you own a beetle with an 8v engine as mk 1 golfs are water cooled not air cooled.

Haven't had timing checked, shall get that done.

And I know mk1's are water cooled not aircooled I'm not a complete idiot!!