Just got done swapping a STI short block into my wrx powered Legacy. Running a Link stand alone computer, currently in a rough state of tune so I can break in engine before dyno tuning. The engine has been running really well, but due to the temp. hovering around 0 deg., morning start-up has been a biiitch. For the first week I would just crank it over and over and eventually It would start with cold start and warm up enrichments about maxxed. Aside from running the battery dead every time, I also had to replace fouled plugs every few days. Some suggested starting fluid. It seems to help, but I 'm not sure how good it is for my engine. Any input.(not sure what forum this should go in. please move if necessary)

Not good for repeated use.

...and ya might wanna figure out the issue so that ya don't wash the cylinder bores.....too much fuel can kill an engine

Starting fluid (ether) is very hard on things. our shop has even seen con. rods bent by the stuff. ( inproper use ) I think you should just try to fix the problem. cold weather should not make your car hard to start, and a with a new engine, the last thing you want is the rings washed down with fuel.

agreed, you are getting WAAAAAY too much fuel most likely, and possibly doing damage in the process.

Wash the cylinder bores? Please explain.

Washing the bores means too much fuel going into the cylinder washing off the lubrication from the cylinder walls. Not to state the obvious, but you obviously are not running right and need to get tuned immediately, or at least get some "safe" map from a tuner. Starting fluid (mechanic in a can) is not a substitute or a fix for anything and should only be used as a last resort, not an every morning ritual.

The car was tuned by a reputable tuner this time, but just to break in engine, we just drove around for a little while under diffrent acceleration conditions and he gave it a "safe" tune. I am not driving under hardly any boost. The car runs pretty good other than starting. One distinct thing it does is back fire when I'm trying to start it, but not when it's running.
After I crank it a few times and then stop, there's a second or so delay and then a loud bang. The longer the duration of the cranking over the louder the bang. The place I get it tuned is far away, so I can't make return visits every day for them to tune it from a cold state. The guy I bought the Link from told me a air temp. sensor wasn't necessary on a Subaru, so I never installed one. Would that help my cold start situation?

The car was tuned by a reputable tuner this time, but just to break in engine, we just drove around for a little while under diffrent acceleration conditions and he gave it a "safe" tune. I am not driving under hardly any boost. The car runs pretty good other than starting. One distinct thing it does is back fire when I'm trying to start it, but not when it's running.
After I crank it a few times and then stop, there's a second or so delay and then a loud bang. The longer the duration of the cranking over the louder the bang. The place I get it tuned is far away, so I can't make return visits every day for them to tune it from a cold state. The guy I bought the Link from told me a air temp. sensor wasn't necessary on a Subaru, so I never installed one. Would that help my cold start situation?

...almost certainly