 1999 P71 w/poor horse power
I have 1999 P71 with poor horse power, recently I replaced the factory cats, O2 sensors, mufflers and air intake system with Walker cats, Bosch o2 sensors, super 40''s and a K&N air intake kit.
Would a mass air flow sensor be faulty or a PCV valve, causing loss of horse power, would the check engine light come on, being it''s an electrical unit?
Also, around 30 - 50 when I'm driving at a steady speed the car does this little uh every few seconds...? Almost like trying start car with a dead battery.
How can I pin point the problem?
What other improvements can I make?
(Currently the check engine light is not on.) | 
