Progress Thread Added Plenum And 75mm Throttle Body Today

Today, I added an aftermarket upper plenum and 75mm throttle body to the old 215k mile GT. I found new-unused parts for a good price, so I jumped on it... they are made by professional products.

The install was smooth. As others, I had to clean up the hole for the throttle return cable. The throttle retainer bracket didn't fit as nicely as factory either, but it works. Seems like the parts made a nice difference in power. The throttle is obviously more touchy in normal driving. That's probably a good thing during the hot summer with the AC on, but I am not sure how it'll work out in the snow yet. I am not sure if it gained any mid range torque as many see, but I do notice it runs out to red line a little better. From what I read before, if my NPI didn't have the other mods, it wouldn't make much difference.

I guess I have accumulated a good number of mods now...
PI intake
PI cams
offroad H pipe
tuned (TwEECer)
underdrive pulleys
drop in K&N
removed air snorkle
Seems like I am just about out of easy "bolt ons". I would like to add PI heads sometime, but I don't see myself dealing with long tube headers. The difference in power from stock is dramatic though. The stock NPI would run out of breath by 4500 and had little chance of breaking the tires loose from a roll, even in first gear. Now, it'll rev out much nicer and make a scene in first if you aren't careful.

Here are a couple pictures:

StanglovR1 said:

looks good for an old girl! get some gears and she'll break those tire np

Click to expand...

Thanks. I try to keep her up, but she is a daily driver and sees it all.

I always felt the stock 3.27s were a good match for the NPI. There was no point in reving above 4500, so the shift points seemed fine. Now that the power band is shifted up a bit, it'll rev to nearly 65mph in 2nd . It kinda limits the number of gears you can play with on the street. So yeah, some 3.73s would be nice. As it sits now, it takes a good surface to hook 1st from a roll. Anything else varies between getting completely sideways and a long squeel, depending on how bad the surface is. good times.

I could make use of the 555Rs and nitrous bottle just sitting in my garage. Any one have a window switch for sale cheap? Oh, the fun I could have if it didn't need to be daily driven....