Extremely high rpm's in neutral

Have you checked for a broken valve spring. Repaired a dodge engine with the same running issue as you have described and it was a broken intake valve spring.

Have you had fuel pressure tested, as well as exhaust for possible plugged catalytic converter?

Check the air intake sensors, called MAF or MASS air flow. They have temp and baro devices in them.

when checking the transmission fluid always check it while vehicle is running, if you overfill the transmission YOU WILL BURN IT UP. secoundly the high RPM is most likley a cause by a bad TPS Throttle Posiction Sensor. and yes the high RPM can cause transmission damage if you do not fix the problem pretty quick .in this case good idea to do soits getting harder and harder to get parts for these cars TPS-25.00 to 45.00 if you fix it your self, simple to do

I looked at info for 1500--5.7L engine.
6 psi @ 1000 rpms
18 psi@2000 rpms
24 psi @ 4000 rpms

Sometimes, you can use analog gage in place of oil pressure sending unit and double check oil pressure that way. If oil pressure is actually low, if high mileage engine, I doubt replacing oil pump will help. I just wanted to add, check oil pressure engine warmed up.

At 4000 rpm what does your speedo say. Your computer may be limiting both your mph and your rpms. I have a 2004 Ford Ranger at 90 mph the engine sputters and seems to miss. It will stay at 90. In neutral it revs fine. My problem is because of chip programming in the computer. Your problem may be the same.

You most likely have an air leak in the intake tract. Check and make sure your vacuum hose or hoses are attached also check for air leaking into the intake behind the carbs. When the bike is running, spray carb cleaner between the rubber boot and the engine. If engine changes rpm you found your leak.

First impression was why would anyone rev their motorcycle to 9 grand in neutral? I could see if you were in gear clutch pulled and ready for a "drag" or Race Start but in neutral?

Anyway I can't hear it so if the sound is like it hits 9k and starts popping then two things either an over rev limiter which I doubtr because the engine red lines at 13,500 OR you have a set of spark plugs breaking down under load

there is a tps located on the intake where the inlet tube for air intake connects, it would be on the left side of the throttle body. does the trk run rough on idle? up/down sputter sometimes stall? Is check engine light on? if no light,check all vacuum lines for cracks/splits loose fit. do this by spraying carb choke cleaner on connections motor rpms will change if leak is present. also spray around perimeter of intake housing where mates with lower intake if engine revs you have bad intake gasket.I Just replaced upper and lower intake on my 98 and shazaam, runs like it should. but do your checks first,unessasary fixes are costly and **** you off.

Yes, the PCM for your vehicle's engine has a rev/speed limit seeting programmed into it. Most stock, non high performance/police package vehicles usually won't go above a top speed of 97MPH. if you were to rev your engine while it was in park or neutral, once the engine reaches the cut out rpm limit preset in the PCM, it will cause the engine to cut back, then it will rev up until it hits the preset limit, then cut back, and it keep repeating that pattern. It may sound as though you have a high rev ignition failure that sounds like waaa, waaa, waaa, waaa, but that indicates the PCM is doing its job.