The metering block is held in place with tamper-proof torx screws.  I could not find a part number for the metering block, but I was able to find the formed o-ring that seals the metering block to the carb body.  The metering block houses a non-replaceable needle jet, so having the ability to remove the metering block might come in handy.

Extend the cable slot to the second hole.  A hacksaw works good for this job.  Be careful, don’t saw too deep.  Maintain the same depth as the existing slot.

Another option is to modify the stock throttle cable.  Fast650 has done that on his PWK38.  He shared these pictures with me.
 
He files down the cable elbow so that it will fit in the socket on the top of the carb.

You need a new airboot to attach the PWK to the stock airbox.  I used a 2” rubber pipe coupling and made an adapter out of an ABS fitting.  It all fit perfect; looked factory fresh.  Before you install the boot, you have to make sure that the slide goes all the way open when you twist the throttle to the fully open position.  Adjust as necessary to achieve WOT.  I believe Fast650 overame the airboot issue by turning his stock airboot around.  Again, check with the Fastman for specifics.   It’s an easy mod.

This Ideal 5/16” wide #32 stainless steel worm clamp does the job.  The stock clamp has limited range.  The picture shows the Ideal #32 clamp on the top and the stock clamp on the bottom.

I already had a good idea where the jetting should be.  As delivered, this carb is way too rich.  It had a #55 pilot jet and a #160 main jet.  I changed the jets before I installed the carb (#40 pilot jet, #140 main jet, needle clip in center groove).  The K&N flat panel filter was in the airbox (sans cover).  Ready to rip.

It started right up and ran good.  Idle was a bit rich but overall, it felt good.  After a bit of grooming, it was dialed in.  Under normal cruising conditions it ran perfect.  Easy to start, smooth idle, great throttle response, no surging, no hiccups, no afterfire (with the exception of a little cackle crackle on deceleration).  Absolutely no KaBooms.
 
Once I was sure it wasn’t too lean, I started doing timed pulls.  It had this unnerving tendency to go rich at high rpm.  Start pulling back on the main jet and things improved up top, but then it would be lean at initial WOT.  No amount of fiddling could rectify the problem.  It sure was looking like the flat-panel air filter was choking things off.  It could flow enough air at the lower rpms but couldn’t keep up as the engine speed increased.

The PWK couldn’t match the stock carb.  That just didn’t seem right.  Could the stock cylinder head be limiting flow?  Possibly.  But it looked more like the filter.

Let’s look at the setup.  Completely stock engine, airbox cover removed with K&N flat-panel filter element, stock exhaust header, LCGP high flow muffler.

With the stock carburetor this setup ran:

Second Gear 4K to 7K: 3.55 seconds
           
Third Gear 4K to 6.5K: 6.53 seconds
           
Fifth Gear 3.5K to 5K: 5.72 seconds
           
Fifth Gear 3.5K to 5.5K: 9.19 seconds


With the PWK carburetor this setup ran:

Second Gear 4K to 7K: 3.66 seconds            0.11 seconds slower than stock carb

Third Gear 4K to 6.5K: 6.64 seconds            0.11 seconds slower than stock carb

Fifth Gear 3.5K to 5K: 7.01 seconds            1.29 seconds slower than stock carb

Fifth Gear 3.5K to 5.5K: 10.26 seconds      1.07 seconds slower than stock carb

You have to cut the top off the airbox.  The arced portion in the front serves as a cradle to help support the filter and elbow.