Where is the Crank position sensor located?

Car was running with a rough idle, stalling sometimes at stoplights. So, I would put it in neutral and give it a rev until it turned green, put in drive and go. If stopped and left it drive, it would stall. Week later I noticed big time gas leak in the line so fixed that and then it started to run slow, with very minimal power to get to highway speeds. Cadillac converter was plugged up (red hot pipe) fixed that and it took away my rough idle problem. Now, I put it into drive or reverse and it immediately stalls out. Help! Also, cannot find the location of the crank position control sensor.