ineeedmorespeed

So I just bought an '89 Z28 wiht a built 350ci TPI. Ever since I bought it there was this problem with "cold start" because after sitting it would turn over after about 5 seconds of crank time, fire up to 1500rpms, but then immediatly drop down to about 400rpms and inevitably bog out unless you gave it a little gas. After starting the car and giving it gas for 1-2 minutes the problem went away and the car start up immediatly with no idle problems...800-900rpms in P everytime.

NOW...we just upgraded plugs, wires and a distributor cap, my friend advanced the timing to about 10 degrees and the car ran fine last night. Today I went to start it and it gave me the usual cold start problem but this time it wouldn't respond to me giving it gas. It would be and on/off sort of thing...I could barely keep it idling about 400rpms and definitely can not drive it more than 10ft before it bogs out?

what do you guys think?

fuel pump...iac valve...tps valve...plugs/wires...anything?

My main concern here is $$$ to fix it. Should I be worried...other than this problem the engine runs fine.


On a side note...I upgraded to Mobil1 synthetic motor oil only to find out from the guy I bought the car from that the motor was not built for synthetic and that running it could cause problems. I've only ran it for about 50 miles but I did a couple 1/4 mile runs...could this cause any problems so soon???

thanks in advance..