That should be about the same thing as a high rise manifold that we used to
use back in the 70's to increase power and fuel economy. Back then we were
very surprised that when we added spacers under the carb, between the carb
and the intake, it actually increase fuel economy and performance. If there
is a way to open up the exhaust as well, such as headers, that will improve
it more than anything else you could do. But I don't know how legal it is to
add headers anymore since the introduction of the catalytic converter. I saw
an article in pop hot rod in the mid 80's where they took Ford catalytic
converters and put them on Chevy vehicles to increase performance, it seems
that at least back then the Ford converters were more open and didn't choke
down the exhaust as much as the other vehicle makers. They may all use the
same converters now though, I don't know, I have not worked on an engine in
30 years.

KY

There is really not much that you can do to that engine to increase its
power.  I'm not sure if there is a power programmer available for that
engine but if there is, that is just about the only simple (but not cheap)
method that I am aware of for that engine.  As for those spacers, with
today's computer controlled fuel injected engines, unless there is a flaw in
the design of the intake manifold to begin with, they have little to no
effect.  Now if you want real power,  you could always super or turbo charge
it and there may be a supercharger kit available for that engine.

Joe,
I have built and driven many high performance vehicles in my life and the
one thing I can say is that it is never simple nor inexpensive. Today, it is
even more complex than 30 years ago. I can also state that the most
effective mod is always cubic inches. High Tech is expensive and the return
is less effective than more inches. It is also safe to say that any money
invested in performance must be considered lost financially. You will never
realize the investment in increased sales price when changing vehicles. So,
my advice is to find a wrecked late model with a 5.9, buy it complete with
gearbox, wiring harness and computer and swap out the 3.9. It will be
worthwhile both in performance and economy, as well as affordable fun.
Steve

   The air spacer doesn't work.  I've never seen a
single dyno sheet that proves it.  There's no fuel in
that area, so all it does is change the air flow.
    In the old days - carb days - getting more power
from a stock engine was pretty simple.  The factory has
a very conservative tune, so you just made it more
"aggressive".  Add timing, add fuel.  That has to be
done by reprogramming the computer.  Check with Jet and
Hypertech.
     Moving the air in and out better is usually worth
something.  The factory exhaust is pretty good.  After
market systems will improve power at the top end.   But
you don't get a lot of nag for the buck there.
     A cold air induction is actually worth some
power.   The factory intake is kinda restrictive.  A
drop in K&N air filter won't help at all, though.
    Another tried and true method is changing the
rocker arms to a bigger ratio.  Increasing the rocker
arm ratio is like adding a slightly bigger cam.
     All magnum engines use the same design rocker
arm.  The 3.9, 5.2, and 5.9 use exactly the same parts.
 But the V-10 uses a longer ratio.  Swap in the V-10
parts and gain some noticeable power.  I have a set for
my 5.9 sitting in the garage waiting for me to install
them.
     Don't forget the non-engine improvements - lower
gear ratio, lower weight, better aerodynamics, low drag
tires.

I have the 2" spacer in my 318 1995 4WD SLT and I also put in an MSD coil,
dual exhaust, Mopar HP computer and K&N filter. The biggest gain was in fuel
economy that went from 13mpg average to 17mpg. Highway milage is almost
18mpg, but not quite.......:-). Torque increased quite a bit too with it not
shifting much on small-medium grades when towing. I just went over 172,000
miles and it still runs great with no oil usage. These modifications have
been installed since it was at about 50,000 miles and the savings in fuel
alone has paid for them several times.