My truck will crank but has a hard time starting?

Alright here is the problem. My truck will crank like a champ but has a hard time firing over. Then when it does start it sometimes has hesitation when pulling into traffic.

Here's what I know:
1. I've got spark.
2. I smell tons of fuel when it does fire over!
3. It seems like some one changed the exhuast and it doesn't have a cat.
4. It may also be missing an 02 sensor but I don't know exactly were it will be located.
5. Sometimes it will fire right up but still seems to run a little lean.
6. When I turn the key I can hear the fuel pump.

Here's what I've replaced:


Injectors
Fuel Rail
Tune-up.

That's about it.
I appreciate any advice you can give me. I'm really frustrated with this truck.
Thanks,
Sarge Kerr

Give us a hint on the age and engine type of your Disco..