Generally easy starting when cold and hard when warm can be a couple of things.
1. Fuel filter or fuel pump causing low preasure--check with gauge.
2. Fuel injectors dirty because EFI adds extra fuel to when cold--clean them.
--Clean with tool thing and compressor:
https://www.youtube.com/watch?v=bKGI9N_yWd0#aid=P-7g8avjiXM putting
the cleaner in the tank often makes it worse.
--Clean them out of the car--much cheaper:
https://www.youtube.com/watch?v=7aT4S1lIBAY
Search on you tube for other methods.
--Fuel Injector Pigtail Wiring Connector Plug 83-91 VW Vanagon T3
Transporter--go to junk yard like I did to get one:
http://www.ebay.com/itm/Fuel-Injector-Pigtail-Wiring-Connector-Plug-83-91-VW-Vanagon-T3-Transporter-/351008673391
--VOLKSWAGEN VANAGON Standard Motor Fuel Injector O-Rings SK3
http://www.summitracing.com/parts/smp-sk3/applications/make/volkswagen/model/vanagon

All that being said you probably have a leak in you fuel system like
o-ring, stuck open injector hoses  return or
! Fuel pressure regulator do test bellow !
http://www.ehow.com/how_7300305_test-fuel-injection-pressure-regulator.html

I don't think it is your fuel pump if it initially comes up yo
pressure when running.