I just picked up a 1995 T100 4x4 with the 3.4L V6. When I bought it it did have a bit of Pre-ignition (spark knock, dieseling) occuring. It also had a extremely cold A/C but needs the resitor pack for the blower speed control. I just replaced all of the spark plugs, fuel filter, put a K&N Filter in it, cleaned the throttle body and MAF sensor, replaced the PCV valve and grommet, ran sea foam through the intake and in fuel tank along with injector cleaner, had the timing belt replaced, added water pump lube to antifreeze.

The questions that I have are...
1. What else besides the plug coils and wire/boots could be causing the pre-ignition problem. How can I tell if this engine is equiped with a EGR Valve?

2. My A/C is now just warm and the prior owner had the A/C system recharged prior to sale. What could be causing this? I know tha the HVAC Blower only operates on High so the resistor pack probably needs replaced, unless the wire isulation is melted and then needs repaired/replaced.

Any information that can be given to assist in the repair of the problems is greatly appreciated.