I installed one on my truck a couple of years ago. Not worth it. The exhaust system is 3" into the muffler and 3. 5" out. I think there are other companies nowadays making them 3. 5" to muffler and 4" out for $200-$300 less.
The 14cm wastegated housing is also available for less from other vendors.
If you don't plan on BOMBing big time don't buy the intercooler (MO). When I installed mine I noticed no improvement via gauges, G-TECH, or my seat of the pants feeling. Although they told me REPEATEDLY over the phone the intercooler would add 30hp by itself (yes i was skeptical since it didn't look much bigger than stock and cost the most $895) it wasn't until I read in the instructions that you need to turn in your fuel screw 120* to benefit from the intercooler. I could have done that without the new intercooler and realized the same improvement.
For guys with a non- intercooled truck (89-91. 5) I HIGHLY recommend the intercooler.
Overall I gained about 1. 5 psi boost from the exhaust and lowered my pyro by 100*
The 14cm housing gave me about 3-4 more psi, 200* less on the pyro and much better spool up. This was at 6100ft elevation.
On a positive note the Banks system is quiet, easy to install, has good instructions and makes no black smoke. The biggest improvement was the 14cm housing.
If I did it again I would buy the bigger, cheaper exhaust, switch to a MUCH cheaper 14cm non-wastegated exhaust housing($425 vs. $170), and enjoy the same benefits above for less than $900.
I would then save the $$ and tweak the pump for free and gain A LOT more power and increased smoke. If you still want more buy injectors, bigger turbo, port and polish the cylinder head... etc.
I almost forgot the gauges. Do that first. They can be bought from almost any vendor on the TDR website and you can watch the results as you increase your mods. A pyro and boost gauge is a must but I also opted for the tach & transmission temp.
If you're wondering about the wastegated housing, I elected to leave mine disconnected since my truck could only muster 20psi (the Banks is pre-set at 21psi). It wasn't until I started messing with the fuel screws that I could exceed 21psi but by then I needed more than 21psi to keep smoke manageable and the pyro temps safe.
I realize this is long, but hopefully anyone with a 1st gen truck considering a Banks system will read this first.
My truck is a 1992 W250 ext. cab 5spd 3. 54.
Kurt