Alright so my mechanic swapped another 3.5 in for me and the car is running like crap and its idling bad and it has no power at all , doesn't even spin first gear if you floor it.... When u start it struggles to turn on .. Is the timing off? What's going on?

 

Maf? Vacuum leaks? Fuel pressure? rule the easier things out first, then go yell at him for not setting the timing right lol