I got done installing my jspec last weekend. All emissions equipment was kept. Only things not present are the sensors that the jspec does not come with. With the low compression/blown coolant seal/burning oil engine I had in there before I was getting about 17 MPG. With the jspec I am getting about 7-8 MPG with the exact same driving habits. The car accelerates very smoothly all the way to 7000 RPM and beyond if you ask it to. It idles very strong at 700 rpms, no bouncing or searching or anything. The spark plugs are very nice and new HKS Iridium ones, the plug wires are the same ones that were on the car before. I do have an exhaust leak between the turbo and first cat, but that was also present before the jspec went in. I am really not sure what could drop my gas milage down 10mpg. Any insight is appreciated.

 

Maybe the injectors are not stock. That would make sense.

 

So I take it you're not using an TII AFM?

 

The injectors were stock. The tips were a different color, but the numbers matched the ones on my original engine.

 

I do have a TII AFM, this was a direct Turbo II --> Turbo II Swap

 

how do the spark plugs look?

 

So you're using over double the gas to basically get the same power? I'd be checking for fuel leaks... Of course, if you have a sense of smell (I don't really), you may have already discounted this.

 

Spark Plugs are very new iridium ones like i mentioned. The car is definetly using doulbe the gas, you can practically see the needle going down as you cruise down the highway.

 

leaky injectors maybe

 

The car doesn't flood and idles very well... I would think leaky injectors would cause at least one of those things to happen. The injectors also looked to be in very good shape, I know looking at them won't tell me much but the entire engine was very new looking and in better condition than I've seen most imported engines.