I used to get about 4 1/2 for a maximum out of the supercharger on my gauge. Now I can't reach 3, but gets really close. Any idea what could be wrong?

 

Air filter or partially collapsed inlet tube or belt slippage??

 

it may be time to rebuild your powerdyne.. take the belt off and check for play.. my powerdyne gives me 7ish psi max..

 

Were you getting the 4 1/2 in cooler weather? If air temps are pretty hot where you are, that may be what is happening.

 

I think I would first check for leaks.

 

Low boost could be a number of things. First I would try what has already been mentioned such as checking that the unit is functioning properly and wasn't rebuilt.

An easy way to find if it is the filter or inlet, would be to take it off on a clean road and open it up. If you see a sharp gain in boost, that would be were a potential problem would be. If that is the case, the best answer is to have a exhaust shop fab you up the largest metal inlet you can fit to the supercharger being as short distance as you can to connect the largest K&N air filter you can squeeze in.

If that is not your problem, and you still are seeing low boost, it would be more likely that you have a boost leak somewhere, or if you have covered that basis, perhaps a slipping belt. Tensioners are a good fix for this.

And the obvious; a hot and humid day will rob you of a couple of pounds of boost compared to a cool dry day.