Audi A4 b5 1.6 ADP poor performance, RPM needle problems, starts 2nd or 3rd time when cold

Hello! I am new to the forum, and through lots of efforts of searching and to no avail, I hope that maybe you guys can help me with the problems I got.

I have an Audi A4 B5 1.6 ADP manual, FWD, and the problems I have are:

1. Not so good acceleration. Trying to reach higher speeds feels like it takes and eternity..
2. Car no matter if in neutral (WOT) or in gear (WOT) cant go past 4k rpm, and if you keep trying to push it through the engine feels like its about to explode (engine heated up of course). The rpm needle just stumbles at the 4k mark and is trying to jump it over but can't.
3. If trying to start the car when cold it sometimes starts from 2nd or 3rd time with a bit of hesitation, or sometimes starts right away.
4. When letting off of the gas pedal, the rpm hesitates to go down normally, it kind of stutters. And when you depress the clutch pedal, the rpm needle also falls down very slowly.

I have used VCDS-lite to check for codes, couldn't find any. No engine check light also.

I suspect maybe the cranckshaft position sensor is going bad?

The coolant temperature sensor has been changed, thermostat was changed, MAF got cleaned, throttle body isn't clogged up (moves nicely), Air and fuel filters have been changed not so long ago, oil was changed rather recently too. Spark plugs were changed too.

Any suggestions or insights about this problem will be much obliged.

Try checking for an un-metered air induction leak. ie: Air entering the engine other than the intake route. Check hose and Manifold joints. This is a suggestion. Sometimes an induction leak can cause some of your issues.

I have a crack on of the pipes of the exhaust manifold, do you think that could contribute to the problem?

That wouldn't draw air into the cylinders so shouldn't be a factor in your issue.

change the camshaft sensor firstly

Do you have an idea where I can find it on the car?