I'm looking to get another test kit preferably a master with several test in one "package". i'm a little unsure of the nitrate kit i have now its the TetraTest for nitrate and the results i get with this kit are inconsistent. I can do 3 tests and get 3 different colors and and 2 of those test will be in the "acceptable" range. I always take the side of caution and do a water change anyway. But to the point of my question are they any "prefered" manufacturers to use (API, Seachem, etc)

There are many, and I often find I like different brands for different tests. Part of this is that depending on the color transitions for some tests, I find it harder or easier to read.

Something you may want to try with your current test kit, as from a chemistry perspective, the kit should provide consistent results (even if not absolutely correct) if you use it in a consistent manner. I find myself sometimes getting different results than I expect and I go back over my testing methodology to make sure I'm following all the best practices:

Make sure your glassware (or plastic) is clean. Rinse it out after each use, and then rinse it with the tank water your testing before you start a test. If it looks dirty, or has a film on it, either try to clean it more, and rinse it well, or get a new vial.

Always shake up the reagents, even if they don't explicitly say it on the instructions. I've had times when tests came out different because I didn't have the reagents mixed well when I started. I always give them a 5 second agitation even if the instructions don't mention it, if they do, I follow what they say (i.e. they may say to shake the bottle for 30 seconds before using).

Always hold the bottle completely upright when you make "drops". The drop size can vary if the bottle is tilted and watch for bubbles in the drops that may make a smaller or larger drop size. If you see this, start over, it's likely your drops will be off and the results will be skewed.

Measure your water very well. And be consistent with it. If it calls for 5ml of water to test, make sure it's 5ml. I use a syringe to get exactly 5ml (or whatever the test calls for) and then use that to fill the tube.

When capping and mixing your tests, especially for those that require mixing for each drop of reagent, be careful to shake down the tube before uncapping, to not lose a drop every time you take the lid off. Or instead of shaking (if it doesn't say you have to shake), just swirl gently to mix, keeping the fluid in the tube and away from the cap.

Test at the same time of the day, this is most important with pH tests. Tank pH will vary depending on the amount of time the lights have been on, etc. and if you test at different times of the day you are likely to get different results.

If your test kit is hard to read in the range you need (i.e. can't tell the difference between 40 and 60 on a Nitrate scale), dilute your sample with R/O water by 1 to 5 (1ml test water, 4ml R/O) or 1 to 10 (1ml test water, 9 ml of R/O), measure out the amount you need (i.e. 5ml for the test) of the water you've diluted, do the test, and multiply the results by 5 or 10. This can sometimes help if your having trouble getting a reading due to the colors being too close together.

My own experience is that I've had good results with Salifert for Nitrate, though it can be sometimes hard to find. It reads very low range, and is accurate. I've also had reasonable luck with Red Sea Nitrate. I use Aquarium Pharmaceuticals for Calcium, pH, and kH, and don't worry too much that they aren't always accurate, I look for changes week to week. My perspective is that if my tank read CA of 400 last week, and everything is happy and growing, then I'll try to keep it at 400 on that test kit, even if it's actually 380 or 420 or whatever. Hobby test kits aren't known to be that accurate, especially the lower cost ones, so I use them to look more for trends, not absolute values.