startup issues

Ive got a 95 z34 Ive had repaired a leaky water pump, rear brake assembly, Ive had a tuneup, battery, belt, and altenator. Ive even had my intake recently taken apart and cleaned out and a problem I keep having is after my car has sat for @8 hours when I start it up the rpms idle up and down and then finally my car dies and I have to start it up again. It does this 3 or more times before it runs fine. Cant pin-point the prob. any automotive genuises out there??????Also was thinking about swapping my engine for a ss engine good idea....bad idea???

Most people with a w- tend to do a l67 swap which is the 3.8L supercharged motor gm makes. I know it is in the newer grand prix Gtp's.
it fits in the engine compartment pretty easy and depending on the series of the motor the horse power ranges from 240 to 280 the series 2 boasts 240 while the series 3 boasts the higher pony count. a decent informative site i have found is:

http://www.l67swap.com/

They have a decent amount of information and provide a few services such as splicing wiring harnesses and the axle parts you'll need.

if you swap in an ss engine you will have a lot less problems with a 3.8.

your prioblem with the "searching" problem is the air charge temperature sensor, it is located on the intake hose between the air box and the throttle body. this is common with these motors for some reason. i put a my Snap On scanner on mine and i narrowed it down to this. the way it works is the temp sensor has a default mode so when it is cold it shold read -40 below. if it goes bad the unit will automatically read +70 above 0. this screws up the computer because the coolant temp sensor is reading 18 degrees but the air temp sensor is reading 70 above 0 so the two end up clashing and the computer sees 70 degrees and shuts the fuel down but the engine is really cold so now the engine starves for fuel(this is the idle searching problem). once the two start to equal off the car runs fine because the coolant temp starts to rise and meets the temp the air sensor is reading. change this $14.00 sensor from any GM dealer and the problem will be solved. it will take you all of 2 minutes to change this item it pips out of the hose,pop the new one in and re-connect the sensor.