IAT sending unit
 

several people have told me if I insert a transistor into the plug of my IAT(intake air temp)sending unit it will give me a significant power increase, is this true and is it safe if it is???

no and no.

it's a trick with many cars to use a resistor but I can't see how it's safe to fool the ECU into doing something which is wasn't programmed to do...

Seriously Nubee, I think you are hanging out with the wrong crowd.
I would not be surprised if these same people taped a sheet of paper to your back that reads "Kick Me"

I instaled that resister on my 86 fc, what the seller said is that it tells the ecu the air coming into the motor is 32 degrees farenheit, the car gained 12hp, but has a rough idel on hot start. for the old fc it was the best 20$ mod I ever did. There is no way in hell I would ever do that to my 8. Oh and some of the "chips" on ebay will just fry the sensor so be carefull as to which one you get. the biggest gain was in low end for 2.5k to 4.5k.

Yah, a resistor is one thing but chips really only help in significant, consistently measurable ways, with cars that are detuned from the factory. Most commonly this would be turbocharged engines like VW's 1.8T, 2.0T or TDi diesels or some of the domestic turbo diesel pickup trucks. They usually have revised boost levels and fuel maps.

The best a tuner can do with a NA engine would probably be revised fuel maps and timing.

In either case, an actual reprogram of the eeprom in the ECU, commonly referred to as a "chip", is not something that anybody who knows what they are doing will charge $20 for. There's just so much time, equipment and specialized work involved in decoding the original data, altering that data and testing it on a dyno for reliability and effectiveness. The cheapo $20 "chip" that you will find on eBay are very much "not Scottish".