If you do DIY, really read up on everything you need. Source a turbo. Source an intercooler. Buy or build manifolds (or modify stock ones to work). Build your intercooler piping and buy all the various fittings you'll need. Then you need to to think about engine management. Some cars it's as easy as getting a remap of some sort. Others you'll need a piggyback on the stock ECU. Others, you'll need a full on standalone ECU, at which point you'll need to have someone tune it or tune it yourself. If it's not something that often turboed, bet on having to go for the last option. For the first 2 options, remember that MAF location can be critical on some cars. You'll need to buy some ARP head studs. Depending on how high quality an OEM head gasket is and how much boost you want to run, you might can get away with a stock gasket, or you might have to go for some heavier duty aftermarket one. If not, you will have head lift issues. Figure on building a full exhaust system if you actually want it to breath. Depending on how strong the stock parts are, expect to throw forged rods and pistons in once you reach the threshold of the stock parts. That should at least cover the basics.
Almost all of the turbo experience I have is with friends' cars. Some have had good luck. Others bad. My buddy DIY'd the kit on his E30. Some kind of Garrett, ebay front mount, home brewed manifolds, ARP's, megasquirt, home-brewed 3" exhaust, etc. He still had head lift issues. A year ago, he decided it wasn't worth the hassle and took it back to NA.
Another friend has a 94 1.8 Miata that's turboed. A full-on 3+ grand Begi-S kit. Garret 2554 turbo, ebay front mount, enthuza 3" SS exhaust, megasquirt, It runs good but we've had to play with megasquirt quite a bit to get it that far.
Another friend has a 240 with an RB25 swapped in. Stock turbo, stock ECU, ARP's and turbonetics metal head gasket. Greddy-style log intake manifold. Aftermarket front mount. He has major boost problems that he's chased for nearly the past year.
Remember, the potential for boost leaks are everywhere and can be such a pain to hunt down. I wouldn't jump into a turbo car unless you really knew what you were getting yourself into.
Edited by Lurch, 06 September 2013 - 07:58 AM.