All I can think of is Trial & Error.
Check the converted .map file in the SAMP folder and removed X ammount of objects. Test The map, if still crashes, remove X more objects, but put back the ones you removed.
This could narror it down to what objects are causing the crash.
For future builds though, try to make the base of the track first.
- 1st : Roads
- 2nd : Blocks (Fences, Blackades, Barriers)
- 3rd : Realism Extras (Lights, Flowers)
Then after each stage of devlopment, test them. Test roads, test roads+Blocks, test roads+blocks+extras.