1998 2.5 Power Loss
 

Having just rebuilt the engine due to damaged cylinder liner the engine now cuts out around 5,200 rpm. The car has been down for app. 12 months. Mexhanic states reason could be lack of fuel pressure.

Any idea and/or suggestions?

Start from square 1. Plug in an OBDII reader and read out the codes. It could be 100 possible reasons but error codes will narrow the field. If you need a second opinion from a qualified Porsche tech in SD let me know. There are several highly qualified shops there.

1998 Boxster 2.5 Power Loss
 

To Topless
Thanks for the response.
The vehicle is with Mark @ Performance Porsche in Mission Valley, and he has worked on tons of Boxsters over the years.
He has checked all possible codes, the reading is a non-specific engine error code.
He has driven the vehicle on both freeway and surface streets with the same result, misfire and consequent stall.

Could be a lack of fuel pressure? Try pressure testing it... Its super quick and relatively painless, and it will at least point you in hopefully the right direction... If not fuel pressure, next to check is probably cam position sensor. Then maybe MAF?