need help... car has no power, revs really slow

[TSisleeper]

my friend just bought a 91 fwd turbo 5 speed. the problem is that the car rev's very slow and only goes to like 3K on the tach, now this is strange becase the car has only minor mods and the turbo spools, but it only makes 3-6 psi and acts like it's hitting the infamous fuel cut? the car has 173K, as does the motor

MODS:
fmic with 2 1/2 inch piping
k n open air filter
all the free mods
removed a/c system
oil press and boost gauges

This weekend were doing a compression test and checking timing, anything at all would help, suggestions, checks, ideas, on and by the way the check eng, light came on today so he's going to be replacing the o2 sensor and I mentioned about replacing the fuel filter also. I think this only could be a timing or fuel problem, possibly a head gasket?, how do you do a leak down test, does it have to be done at a dealership / by a mechanic? I'm now starting to think also that the rings are bad because I rode in the car for the first time today and I noticed some blue and black smoke, checked the turbo, no shaft play, also with the fuel cut thing I was thinking maybe a boost leak tester from home depot ? just need help. thanking you in advance...... Jace

 

[The_EE]

Check for boost leaks and vacumme leaks.

http://www.vfaq.com/mods/ICtester.html

Could be fouled plug, maybe bad injectors.. there is a whole list of things to do.

As for the oil problem, could be oil being blown through into the intake, how clean is the intake on the car?