Backfire and hessitation

My 2003 P71 has been acting up on me lately. When the motor is cold it frequently backfires through the intake when under partial to full throttle. Just tonight I went to stomp on it from a stop, and the motor almost died. The motor was just starting to rev up and then it hesitated real bad. I'm hoping it's just the DPFE sensor. Might someone have any other ideas?

Thanx.

One more thing I forgot to mention. Under partial throttle I hear a whisteling sound from under the hood, kinda sounds like brake squeal.

ive noticed a whistleing sound on my 99 P71 during the high revs, and it doesnt sound like belt sqeal but i cant figure it out. if you find the prob, let me know how much to fix, and what difference it made. Im trying not to fix it if it aint broke, you know what I mean.

ive noticed a whistleing sound on my 99 P71 during the high revs, and it doesnt sound like belt sqeal but i cant figure it out. if you find the prob, let me know how much to fix, and what difference it made. Im trying not to fix it if it aint broke, you know what I mean.

I'll be doing some work on my Vic on the weekend. I'm going to take the throttle body off and the upper plenum and clean them out. I'm also going to install some MDS coil over plugs, and an Airraid throttle body spacer.

My theory is that the throttle body is causing my squeal. The engine only whistles for me at certain throttle positions, and from what I can tell only when the enging is under load.

I'll let you know if solve my problem.

Relpaced the DPFE sensor which for 2003 is part of the egr valve/tube. Cost me $270 canadian and I replaced it in about 15 minutes. Just gave the EGR connection a little dab of heat with an oxy acetelyne torch and it turned right out.

Hesitation is gone.

put on the MSD tonight. I had to modify the coil overs because the MSD are about 1/4" taller that stock. The MSD needed room to clear the fuel rail on 3 coils. The rear drivers side, the front passanger, and the rear passanger cylinders.

I'm not sure about how the MSD performs yet. I disconnected the battery for the project, and I think the PCM needs a bit of time to relearn. So far I can't feel any seat of the pants difference although the car does idle smoother and with less variatio in idle RPMs.