i just had my engine rebuilt by a shop. now i am having a problem running intermittenly lean. i dont no how it acts under boost because i am still breaking in the engine but it my narrow band O2 gage and my apex i turbo timer both show the engine going off the scale lean every now and then. when those gages show the lean condition the car starts bucking and shaking pretty bad.
the ecu is showing the 55 code for all ok. i tried shaking different parts of the whiring harness and nothing was loose. vacume is 18 at idle and 24 at 2000rpm.the only things that changed during the rebuild were forged pistons(stock compression) and the adition of hks step 1 (264/264) cams. any ideas?

my setup:
91 240 w/redtop
300z maf
t3t04e
fullrace exaust manifold
740cc injectors
300z fuel filter
wolbro 255 fuel pump
nismo adjustable fuel pressure regulator
Enthalpy tuned ecu

all parts have 5k miles or less. this problem did not exist befor engine rebuild.

thanks.

aaron

my web page.
http://www.cardomain.com/memberpage/676406