VW Microbus 2.6i when it reaches 3000 rpm revs drop and wants to switch off

SOURCE: can't pass 3000 rpm

need to check codes and see if it has oil in it. and go from here.
if the computer sences low oil pressure it sets a rev limiter to try and save the engine. code P1259 i think. 4 or 6 cyl?

SOURCE: I cannot see at what speed I am travelling and cannot pass 3000 r

there is a either a engine vacuum problem maybe caused by the oxygen sensor not working properly or your fuel filter needs to be replaced.

SOURCE: car drops out at 2700 rpm and sputters

There is a rev limiter in these cars that disallows over revving in park or neutral. Does it climb past 2700 under hard acceleration?

SOURCE: engine will not rev above 3000 rpm

Inadequate fuel pressure, change the fuel filter first, make sure the car sits for at least two hours before replacing the fuel filter because these fuel lines are under high pressure during the time of operation. The pressure usually decreases over time in the lines but wear safety glasses just the same, I would recomend depressurizing the fuel system first, buy a Haynes repair manual for detailed procedure to be safe. If problem persists go to Auto Zone and ask them to check for trouble codes these codes if present may instuct you in detail to replace the MAF sensor or give you a code that must be looked up to find the problem.

SOURCE: p1613 fault code & engine will not rev over

Crank sensor or engine speed sensor is faulty.

Fault:
Irregular power loss on accelerating
The speed of the engine is limited till 2500rpm
Frequent loss of crankshaft position sensor signal

Cause:
It is caused due to leaking from thermostat housing into crankshaft position sensor harness multi-plug

Remedy:
Check and clean the crankshaft position sensor harness multi-plug contacts. Rectify the engine coolant leak from the thermostat housing if found. Take a note of the engine coolant level and monitor it for changes, showing a leak is indeed occurring.