Been having a fuelling issue of late. So had it on the dyno today and found that at around 5000 rpm the fuel leans out. we tried different duties but still the same. So mapped to a safe level until we get to the bottom of what is happening.
So fare my ideas are possible Maf issue, or FPR is naf. Just fitted new walbro 255 but not ruling out this being faulty so ordered a new one. Was told that a batch of 255's have had a fault with split pipes so just in case new one on way. We are going to measure fuel pressure next week to see what its doing and I have a new adjustable FPR ready on order just in case. If anyone else has any ideas please put them forward so we can check them as well.
Car is an MY94 WRX Wagon.

Cheers
Iain

 

Check any vacuum hoses for splits.

 

Oh right will do that.