while i had my upper plentum off today tapping in the boost gauge, i seen that the plentum was SEVERLY restricted by the casting inside it. i took and cut out the extra casting, and smoothed up all the edges. i bet it was opened up 200-300% more just on the inside of the plentum.

we then opened up the inside of the tube, and smoothed out that, then took a cylinder hone and damn near polished the inside of the tub about 9" or so.


right now i am putting the ride back together after a complete paint job, and installed a few goodies while it was torn apart. i have not yet got to drive it, but after we fired it up, it seemed to be stronger just by the sound alone.

i think for an hours work, this will make a HUGE difference? have any of you guys done this as well?

Yeah, I took a grinder to mine too, and swapped a HD manifold underneath. I noticed a difference on the reading from the boost gauge. It used to climb faster, now its just a hair slower, but I interpret this as being the reduced restriction as now the gauge is reading the pressure in the lower manifold rather than the area above the casting.

thats a good way to think about it.


i looked at the VIN, and i have an F code motor, so does this already mean that the intake is HD?

Slower spool-up could be related to your on-going engine problems - when engine is "missing", thermal efficiency will be lowered, with reduced exhaust energy.

No fire, no blow - eh?

...I wouldn't call it slower really, its barely noticeable except that I watch it so closely before and after. There is no miss ever, not at idle or under heavy load, pulls like a dream on the highway and the turbo will easily make ~14psi in under 1 sec.

i noticed today that the boost went to 14 or 15 while still accelerating and then it dropped to 5 or 6 like that. i wonder if the waste gate is comming open to soon? any ideas fellas??

Sounds completely normal, consider the resitor on the Map sensor mod to keep it a little higher if you want, the stock system will try and maintain 5~6 psi.