Alright members I've got a treat for you!!!
If you are comtemplating an air intake system, I've got the $40 alternative to the JWT POP-Charger. Many years before the open air intake systems were popular, I figured out a way to put a K&N cone filter in my 89 240 for more power to complement the S&S header that I designed with Loren from S&S. This works on all S13 body 240s. Here is the parts list:
1. a K&N cone filter: part#RU-2520 (5" long. up to 300hp) OR
part#RE-0870 (9" extra-long. up to 600hp!!!) but a little more $$$
2. a K&N breather for the AIV. part#62-1360
3. bracket material & a zip tie
1. Unclamp (four "G" clamps) the upper air box to remove the stock filter and unbolt (four 10mm bolts) the upper box from the mass air sensor. At this time, unscrew (two philips screws) the Air Temp Thermisensor from side of the upper box and also remove the hose that runs between the upper box and the AIV induction box(square plastic box with molded stripes). Remove Upper Box from the engine compartment and put it on your workbench.
2. Remove the bottom portion of the air induction box. After you loosen the bolts, it slides out of the mounting slot. Chuck this part when you get it out. You don't need this anymore.
3. Now look at the inside the upper box. You'll notice a shiny cadmium plated VELOCITY
STACK, complements of the Nissan factory. You must drill out the aluminum rivets to
separate the Velocity Stack from the upper box. Use an appropriate drill and gun it at
medium speed. This should be easy.
4. Now, position the velocity stack against the mass air sensor (make sure there is a thin black O-ring in between) and bolt it(the four 10mm bolts from earlier) back on, this time without the black plastic upper box. As you do this, you'll notice that the bolts are a little too long. You must shorten the bolt (or buy a shorter metric bolt) so that it
barely protrudes from the mounting nuts that are welded to the velocity stack. If you don't, it will interfere with the air filter clamps.
5. Now, get out your new K&N filter and slip its mounting clamp off. You have to
notch the clamp so that it's concave in the inside. I did this with a crimping plier. Use
your ingenuity on this one, but it has to look some thing like this:
outside--> ( <--inside of the clamp.
6. Clamp the K&N filter over the edge of the mounted Velocity Stack using the clamp that you have prepared in step 5.
7. Oil the K&N Breather Element with the supplied oil pack. Afterwards, clamp the Breather Unit to the hose nipple (where the hose once clamped to) of the AIV induction box.
8. Zip tie the Air Temp sensor (by one of the two mounting holes) to the Velocity
Stack's mounting flange at the unused hole left by the drilled out rivet. *Note: Some
early models and Federal editions did not have a separate Air Temp Sensor. If you own one
of these, then disregard this step.
9. Fabricate a suitable bracket to prevent excessive movement and possible damage.
10. Go race a Honda...
Simon Kim '89 Turbo Coupe
BTW, I bought my Nissan Service manual before I purchased the car, so I got an early start on this kind of stuff. :)